LESSONS FORGOTTEN: ROYAL NAVY ANTI-SUBMARINE TACTICS OF WORLD WAR I

Transcription

1 AU/ACSC/STUDENT#-4577/ AIR COMMAND AND STAFF COLLEGE AIR UNIVERSITY LESSONS FORGOTTEN: ROYAL NAVY ANTI-SUBMARINE TACTICS OF WORLD WAR I by Darin C. Curtis, LCDR, USN A Research Report Submitted to the Faculty In Partial Fulfillment of the Graduation Requirements Instructor: Lt Col Matthew C. Stafford Maxwell Air Force Base, Alabama April 2005 Distribution A: Approved for Public Release; Distribution is Unlimited

2 Disclaimer The views expressed in this academic research paper are those of the author and do not reflect the official policy or position of the US government or the Department of Defense. In accordance with Air Force Instruction , it is not copyrighted, but is the property of the United States government. ii

3 Table of Contents Page DISCLAIMER...ii PREFACE... i v ABSTRACT... vi CHAPTER 1 INTRODUCTION...1 CHAPTER 2 GERMAN U-BOAT CAMPAIGN IN THE EARLY STAGES OF WWI...3 CHAPTER 3 BRITISH ANTI-SUBMARINE EFFORTS, AUGUST APRIL CHAPTER 4 THE EVOLUTION OF BRITISH ANTI-SUBMARINE WARFARE, CHAPTER 5 THE ROYAL NAVAL AIR SERVICE IN THE ANTI- SUBMARINE WAR...14 CHAPTER 6 ROYAL NAVAL AIR SERVICE FIXED-WING ANTI- SUBMARINE WARFARE...16 CHAPTER 7 THE IMPACT OF THE FLYING BOATS ON THE CONVOY SYSTEM...19 CHAPTER 8 UNITED STATES NAVY ANTI-SUBMARINE WARFARE PRE CHAPTER 9 DEGRADING ANTI-SUBMARINE CAPABILITIES WITH THE DEMISE OF THE U.S.S.R...27 CHAPTER 10 GATHERING THREATS...31 CHAPTER 11 CONCLUSION...34 BIBLIOGRAPHY...37 iii

4 Preface In the process of deciding on an appropriate subject for this research paper, I wanted to address a particular concern shared by many officers in the United States Navy s S-3B Viking community. The S-3B War Hoovers, as they are known by their aircrews, were the only fixed-wing anti-submarine warfare (ASW) aircraft organically based on the Navy s aircraft carriers. The Viking community is currently in the process of decommissioning all ten operational squadrons. No comparable ASW asset is on the drawing board to replace the S-3B. The decision to retire the Vikings was a result of the demise of the Soviet Union and the ending of the Cold War. It is my contention that the act of degrading our ASW capabilities in the face of increasing submarine threats from China, North Korea and Iran could prove disastrous. To argue my point on this matter, I have chosen historical lessons learned from the British Royal Navy of World War I in its struggle to address the threat of the German U-boat campaigns. Current strategies and tactics for fighting submarines with air power had their roots in the actions of the Royal Naval Air Service (RNAS). The technologies used by ASW aircraft today were envisioned and introduced in World War I. Finally, air power played a significant role in the defeat of the U-boats as will be demonstrated in the course of the paper. The parallels between RNAS tactics and current ASW tactics are numerous and it is apparent to modern day sub hunters that the lessons learned from the RNAS are being forgotten at our peril. iv

5 The majority of the historical data is gleaned from Paul Halpern s book, A Naval History of World War I. His descriptions of the submarine campaigns undertaken by the German Navy and British attempts to find a viable defense proved very enlightening. Furthermore, Squadron Leader T. D. Hallam s The Spider Web, The Romance of a Flying-Boat Flight in the First World War, gave aircrew descriptions and insight into the first use of air power in ASW campaigns. His descriptions of search tactics, attack profiles and the integration of ASW technologies with the airplane depict the roots of current ASW doctrine. Finally, statistical figures from World War I were directly lifted from The World War I Document Archive, an on-line collection of historical data compiled by World War I historians. An examination of lost shipping data from this archive underscores the impact of air power on submarine success. It is therefore my view that, from a historical perspective, the United States Navy is blindly painting itself into a corner by divesting itself of significant ASW capabilities. It is hoped that this work may serve to remind others of the lessons learned in anti-submarine warfare. v

6 Abstract The United States Navy is currently divesting itself of a significant portion of its airborne anti-submarine warfare (ASW) capability on its aircraft carriers. The decision to retire the S-3B Viking creates a critical vulnerability that is exploitable by China, North Korea and Iran as they aggressively invest in their respective submarine capabilities. World War I offers a unique opportunity to compare the effectiveness of waging war against submarines both with, and without the integration of air power. During the first two and a half years of the conflict, ASW was waged by the British Royal Navy (RN) without the use of aircraft. Significant improvement in ASW followed the introduction of air power during the final 18 months. The World War I parallel applies to the modern era, except in reverse order. The United States Navy combined the most modern technologies, tactics, techniques and procedures for ASW warfare in one carrier-based asset, the S-3B. The Vikings were in effect, the personification of every ASW lesson learned by the British in the Great War. For three decades, the Vikings proved themselves to be highly effective Cold Warriors against Soviet submarines. With the fall of the Soviet Union, they were quickly slated for retirement. The first of ten operational squadrons decommissioned in April, In the interest of trimming military expenditures, the United States Navy has willfully degraded the ability of its aircraft carrier strike groups to conduct ASW missions. The limitations imposed by this decision represent a defensive weakness in the carrier strike vi

7 groups readily exploited by the previously named countries. The United States Navy, at its own peril, is forgetting the ASW lessons learned in World War I. vii

8 LESSONS FORGOTTEN: ROYAL NAVY ANTI- SUBMARINE TACTICS OF WORLD WAR I Introduction The German Navy of World War I introduced the submarine to the world as a highly effective weapon capable of bringing a nation to its knees. From 1914 to 1918, the U-boats inflicted heavy losses on allied shipping and very nearly defeated Great Britain. 1 The Royal Navy struggled for two and a half years to devise an effective strategy to defeat the German U-boats. In near desperation from heavy shipping losses in 1917, the British Admiralty, previously resistant to escorted merchant convoys, authorized their use. Also in 1917, the Royal Navy began to employ air power as an antisubmarine weapon. Flying boats, operating on a Spider Web search grid over the North Sea, demonstrated formidable submarine hunting potential. The subsequent integration of sea planes with the merchant convoy system proved to be the ultimate weapon against the German U-boats. The effectiveness of air power against the submarine was not lost on the United States Navy for the remainder of the twentieth century. As a counter to the submarine threat posed by the Soviet Union, the United States Navy developed the carrier-based S- 3B Viking, a fixed-wing jet aircraft. Designed from the beginning as a submarine hunter, the Viking incorporated acoustic, electronic, magnetic and infrared technologies to detect, locate, and track enemy submarines. The ability to carry four anti-submarine 1

9 torpedoes provided battle group commanders the flexibility to use the Vikings both to detect and engage enemy submarines. The demise of the Soviet Union initiated calls for budget cuts in US Naval expenditures. These cuts ultimately led to the retirement of the Vikings and a reduction in anti-submarine capability in carrier strike groups. The purpose of this paper is to draw parallels between the lessons learned during the World War I submarine threat to Great Britain and the gathering threats posed to the United States Navy by aggressive submarine programs underway in China, North Korea, and Iran. The decision to reduce anti-submarine warfare capability in the face of an expanding submarine threat may ultimately prove contrary to the best interests of the United States. Arguably the important lessons learned by the Royal Navy in World War I are being forgotten. Notes 1 Paul G. Halpern, A Naval History of World War I (Annapolis, MD.: Naval Institute Press,

10 Chapter 2 German U-boat Campaign in the Early Stages of WWI In order to fully understand the evolution of ASW tactics practiced by the Royal Navy during the course of the Great War, it becomes necessary to understand the U-boat campaign undertaken by the German Navy. The first few months of the war were marked by a haphazard effort by the German Navy to define its maritime strategy with respect to the U-boat. Indeed, the first merchant taken by a German submarine, the British steamer Glitra, was not taken until October 20, 1914, nearly three months after the commencement of hostilities. 1 The German strategy could best be described as undefined and unfocused with offensive submarine doctrine yet to be developed. Eventually realizing the potential of the U-boat as an economic weapon of blockade, Germany finally settled on a submarine strategy and officially declared unrestricted submarine warfare in early February Unrestricted submarine warfare marked the German intent to sink without warning any vessels found operating in specified waters. The blockade targeted all waters surrounding Great Britain and Ireland with a specific focus on military shipping in the English Channel. At the commencement of this campaign, Germany averaged six U-boats at sea per day from a pool of 37 completed vessels. 3 This initial campaign against merchant shipping would last until the following September when Germany succumbed to the political pressure resultant from 3

11 the sinking of neutral shipping. The sinkings of vessels from various non-belligerent nations including the United States served to shape world opinion against Germany. Of particular interest to the Kaiser at that time was keeping the industrial might of the United States out of the war. This first unrestricted campaign had devastating effects on British and Allied shipping. By September, Germany had sunk in excess of 1,294,000 tons of shipping with a 20:1 ship-to-u-boat kill ratio. 4 Germany, for its part, lost ten U-boats, primarily to armed British merchants known as Q-ships. 5 The year 1916 marked a shift in German submarine strategy from one of unrestricted warfare to one which operated under prize rules. Under prize rules, U-boats approached target vessels on the surface, demanded their surrender and allowed the crew and passengers time to abandon ship prior to the attack. Attacks were limited to Allied cargo ships while attacks on passenger vessels and neutral vessels were to be avoided. Although not as successful as the unrestricted campaign, Germany still sank over 500,000 tons of allied shipping during the first six months of Tonnage figures began to climb in the second half of 1916 and into the first two months of 1917 with the Allies averaging a monthly loss of 325,000 tons while Germany enjoyed a merchant vessel-tou-boat kill ratio of 65:1. 7 Despite an expressed intent to only attack the vessels of hostile nations, Germany inadvertently attacked some neutral shipping and became the subject of international criticism. Sensing the need to hasten the defeat of Great Britain, the German Admiralty sought and obtained the Kaiser s blessing to resume unrestricted submarine warfare in February British losses quickly climbed to an average of over 600,000 tons per 4

12 month with April of 1917 marking the high point in the German U-boat campaign with 860,334 tons destroyed. By the end of June 1917, German submarines enjoyed a 167:1 kill ratio against enemy shipping. 8 The British Admiralty knew that these kinds of losses were unsustainable and subsequently began to consider different techniques in antisubmarine warfare. 1 Ibid Ibid Ibid Ibid Ibid Ibid Ibid Ibid. 341 Notes 5

13 Chapter 3 British Anti-Submarine Efforts, August 1914-April 1917 The British Admiralty struggled to define the best tactics to counter the U-boat threat. An offensive strategy that actively hunted down and destroyed the U-boats was sought from the first days of the war. The specific techniques adopted in an attempt to accomplish this were more an effort at trial and error. The tactics that eventually defeated the U-boats would not be adopted until Initially, the British utilized a fleet of converted civilian schooners known as the Auxiliary Patrol to sanitize the sea in the immediate coastal areas surrounding port cities. This force of small craft was charged with seeking out and attacking German submarines. The main detection method employed by the Auxiliary Patrol was visual sighting. Their numbers were too small however, and the amount of sea space that needed patrolling too great, for the Auxiliary Patrol to be very effective. Another strategy, albeit more defensive in nature, was the establishment of minefield barriers in the Dover Straights and in the northern channel of the Irish Sea. The idea behind this strategy was to deny the U-boats operational sea space and to protect vital British choke points. This approach however, also failed to produce satisfactory results as the Royal Navy was plagued throughout the war by defective mines and mines 6

14 breaking loose from their moorings. Ultimately, the minefields proved nothing more than a nuisance for German submarines. An interesting offensive tactic involved British trawlers putting to sea in known U-boat operational areas, with a British submarine in tow. Using this tactic, the British sub could remain submerged while conserving its batteries and when a German submarine approached the trawler, on the surface, a message would be sent by connecting telephone line to the British sub and a submarine-on-submarine engagement could commence. While an interesting and creative approach, German U-boats soon became wary of the trawlers and U-boat losses were negligible. Perhaps the most effective British weapon against the U-boat in the first few years of the war was the Q-ship. These were merchant ships intended to deceive U-boat skippers by utilizing hidden arms and a second, specifically trained crew. The U-boat would approach the Q-ship, demand its surrender, and watch while the first crew abandoned ship. While the first crew was abandoning ship, the second crew would unveil the Q-ship s guns and open fire on the U-boat. The majority of the ten U-boats lost during the first unrestricted submarine campaign were lost to Q-ship tactics although the U-boats still enjoyed a 20:1 kill ratio. 1 Of note in these early years of anti-submarine warfare was the Admiralty s reluctance to utilize convoy tactics. The concept was rejected as being too defensive, in nature because it sought to avoid submarines. It was thought that the only honorable occupation of naval officers in a maritime engagement was in the active pursuit and attack of hostile vessels. 2 Mounting merchant losses however, would eventually force the Admiralty to reconsider the use of convoy tactics. Ultimately, the convoy system would 7

15 curtail merchant losses and prove to be the best line of defense against the U-boats. Furthermore, in the last year and a half of the war, the use of aircraft would render the convoy system virtually immune to submarine attacks. 1 Ibid Ibid. 351 Notes 8

16 Chapter 4 The Evolution of British Anti-Submarine Warfare, At the pinnacle of U-boat success in April 1917, it became apparent that the British approach to anti-submarine warfare (ASW) was largely ineffective. Mounting losses demanded a change in strategy and spurred a philosophical shift in Royal Naval (RN) ASW doctrine from an offensive nature to a defensive one. The strategy of attempting to offensively cleanse water space for the safe passage of merchant vessels was replaced by one that would seek to defend the vessels themselves while in dangerous waters. Instead of attempting to actively detect, fix and destroy submarines, the focus shifted to denying submarines the opportunity to track and destroy targets. The concept that a submarine could be rendered ineffective by mission denial began to take root in the RN. The new mindset spawned several new technologies and strategies designed to harass U-boat commanders and to decrease their attack capabilities. From the war s inception, the British had been exploring new technologies in the form of acoustic submarine detection. This led to the development of hydrophones, which are essentially submerged microphones. Hydrophone stations were established at vital choke points along the British coast and smaller hydrophones were deployable from surface vessels. The use of hydrophones, however, merely alerted the British of a submarine s presence; they were not capable of actually locating a U-boat. By

17 however, the technology began to integrate itself with other ASW strategies. The ability to acoustically detect a submerged submarine allowed British commanders to employ other assets to keep the submarine submerged. This forced the U-boats to deplete battery power and prevented them from acquiring a firing solution on surface targets. Although not killed, the U-boats were made ineffective through mission denial. In addition to new acoustic technology, Great Britain sought to further reduce U- boat effectiveness by laying minefields in the vicinity of German naval bases. 1 These minefields were secretly placed by British submarines. This concept reduced U-boat effectiveness by forcing German crews to consume more time and fuel while navigating mined waters. The desired end result of this harassment was a shorter operational patrol time and theoretically, fewer merchant losses. Coincidentally, the strategy was responsible for the sinking of seven U-boats between August and December, The spring of 1917 also marked the beginning of another U-boat harassment strategy. The British began implementing significant sea barriers referred to as barrages. A barrage is a sea barrier that combines the use of metallic mine nets hung from floating barriers coupled with deeply moored mines below the nets. By 1918 the barrage nets also included electronic contact mines embedded within the netting itself. 3 The intended effect was to create an undersea wall to discourage U-boat passage. Initially, barrages were used on a small scale to protect port entrances, but the idea was expanded to protect sea lane choke points. The first significant barrage was established off the Belgian coast and eventually extended to the Dover Straights. These waters were patrolled by destroyers and other small surface vessels in an attempt to force the U-boats to submerge for passage, essentially herding them into the barrages. From January to 10

18 November, 1917, only one U-boat was documented to have been sunk as a result of these barrages while 253 conducted safe passage. 4 To counter this British strategy, the U-boats simply slipped over the barrage on the surface while under the cover of darkness. Great Britain responded further with the use of light vessels which used powerful spotlights at various points across the channel in an attempt to force the U-boats to submerge for passage. The addition of these vessels resulted in 14 U-boat sinkings on the Dover barrage during Although not impenetrable to U-boat passage, the barrages undoubtedly harassed the U-boats and contributed to the safe passage of untold numbers of merchant vessels. The Dover barrage proved to be a vital factor in reducing U-boat effectiveness and in maintaining logistic supply lines between the English and French coasts. Ironically, at the height of the successful U-boat campaign in April 1917, the RN begrudgingly initiated a large convoy system for colliers traveling from Britain to France. 6 Previously, only small convoys had been used to make the beef runs between the Flemish coast and England. Convoys had been resisted to this point under the belief that they only massed merchant shipping into large, easily targeted formations which would ultimately only simplify the mission of U-boat commanders. The convoy concept was further resisted due to perceived congestion in port facilities both at the point of embarkation and debarkation. With all vessels either arriving or departing simultaneously, seaports would be swamped with cargoes and the resultant inefficiencies would hamper the war effort. Finally, a convoy would be limited to the speed of its slowest ship which would create longer passage times and expose the shipping to 11

19 prolonged periods in dangerous waters. The 860,000 tons of shipping sunk in April 1917 forced the Admiralty to test the larger convoy system. The convoy approach consisted of a simple strategy of combining multiple merchant ships under the protection of destroyers and cruisers for a single passage through U-boat patrolled waters. Convoys proceeded along approved routes with specific sail times and typically left port at dusk while timing their arrival at dawn to take maximum advantage of darkness. The convoys also incorporated zigzaging which complicated a submarine s firing solution and reduced its effectiveness. The British Admiralty was astonished at the results of the trial convoy system between Great Britain and France. From March to May, 1917, the British sailed 4,016 individual ship sorties under protected convoy and lost only nine ships to U-boats for a 0.22% loss rate. 7 The results were encouraging enough to institute the convoy system through all waters patrolled by the U-boats. By the end of September, the figures for tonnage lost were in a steep decline and were effectively cut in half from a high of 860,000 tons in April to 354,000 by October. Furthermore, the merchant-to-u-boat kill ratio dropped from 167:1 in April to 16:1 by September. 8 It should be noted, that the convoy system achieved this success not by killing U-boats, but by rendering them less effective. The German response to the convoy system in 1918 was to put more U-boats to sea and to concentrate production on newer and longer-ranged classes which could conduct extended operations at sea. While still able to inflict some losses on Allied shipping, the Germans were never able to repeat the success they enjoyed in early Throughout 1918, the U-boats averaged around 240,000 tons sunk per month and were 12

20 never able to push the monthly tallies over 400, The kill ratio also held steady at 16:1 through the final months of the war. The convoy system proved to be a decisive measure in defeating the U-boat campaigns; however, the convoys were made even more effective with the introduction of air power in the ASW fight. 1 Ibid Ibid Ibid Ibid Ibid Ibid Ibid Ibid Ibid. 423 Notes 13

21 Chapter 5 The Royal Naval Air Service in the Anti-Submarine War The Royal Naval Air Service (RNAS) began to integrate the use of air power in the form of kite balloons and lighter-than-air ships during the U-boat campaigns of The kite balloons were trailed behind combatant vessels and essentially served as extended crows nests for the purpose of sighting enemy submarines or surface combatants at greater distances. conjunction with surface vessels. Lighter-than-air ships patrolled the waters in The earlier detection provided the battle group additional time to maneuver into an optimal position to keep a U-boat submerged. While submerged, a U-boat was slow and effectively prevented from closing target vessels and acquiring a torpedo firing solution. Despite their obvious benefits, the kite balloons and air ships also imposed upon the British a singular disadvantage; while aiding in the location of enemy vessels, they also revealed the position of the British surface combatants. 1 German U-boats, by 1916, had incorporated the use of altitude lenses on their periscopes thus enabling them to sight British aircraft as well as surface vessels. 2 For the purposes of this discussion, both types of aircraft were slow moving and neither contained any offensive capabilities against either surface vessels or U-boats. Their main advantage was in enemy detection, but that detection went both ways. In a 14

22 sense, their use resulted in a tactical draw. The subject is addressed here to make the point that although the initial use of kite balloons and lighter-than-air ships pre-dated the British strategy of U-boat mission denial; it provided the RN with an early glimpse of the advantages gained by reducing U-boat mission effectiveness. Notes 1 Ibid Squadron Leader T. D. Hallam, The Spider Web, The Romance of a Flying-Boat Flight in the First World War (London-Melbourne: Arms and Armour Press, 1979) 59 15

23 Chapter 6 Royal Naval Air Service Fixed-Wing Anti-Submarine Warfare The conceptual use of fixed-wing aircraft as a weapons platform against the U- boats was envisioned from the first U-boat campaigns. RNAS sea planes were initially designed and built specifically for submarine hunting, reconnaissance and air-to-air combat with German sea planes. 1 Suitable flying boats, as the sea planes were called by their crews, did not appear in adequate numbers until the spring of 1917 due to several factors. The British prioritized the building of airplanes for use by the army while the RNAS concentrated on airplanes that could be launched from surface vessels, a technology that surface craft would not possess until later in the war. The first flying boat squadrons were established at Felixstowe Naval Air Station on the Southeastern coast of England in the spring of From Felixstowe, and later from other naval air stations, the Spider Web anti-submarine campaign was launched. German submarines, returning from patrol in the straits of Dover or from the North Sea, were forced around the Hook of Holland and into the more restricted waters of the Helgoland Bight as they transited to their home ports. As part of German standard operating procedure, the U-boats announced their return by wireless communications. Unknown to the Germans, the British had established two wireless direction-finding stations on the English coast which could pick up German transmissions, plot a bearing 16

24 from each particular station, and roughly determine the U-boats position based on wireless cross fixing. 3 The RN discovered that the majority of these U-boat fixes fell in the vicinity of a Dutch light vessel, essentially a floating and stationary light house known as the North Hinder light vessel. 4 With this discovery, the RNAS flying boat squadrons designed a circular-shaped search grid centered on the North Hinder light vessel. That grid became known as the Spider Web. It had eight radial arms extending 30 nautical miles with concentric rings at 10, 20 and 30 miles. The grid encompassed 4,000 square miles and a single flying boat was capable of searching a one-eighth pieshaped portion on a typical sortie. 5 When a U-boat broke radio silence to announce its return, a wireless cross fix was generated and a flying boat was launched to that particular portion of the spider web to find and attack the submarine. Flying boats initially carried four 100 pound, (later 230), bombs each with twosecond delayed fuzing to allow for water penetration up to 60 feet before exploding, hopefully in the vicinity of the submarine. 6 Typical attack runs on the submarines were conducted at feet in a level flight configuration flying up the wake toward the stern of the surfaced U-boat at speeds between 60 and 80 knots. 7 In the first month that the Spider Web was employed, the flying boats sighted seven U-boats and attacked five. 8 During the entire Spider Web campaign, spanning the rest of the war, 40 flying boats sighted 68 U-boats and bombed The campaign was particularly effective in the final six months when there were 26 sightings and 18 attacks. 10 The Spider Web campaign conducted by the flying boats of the RNAS succeeded in harassing and destroying enemy submarines from April 1917 through October

25 While it is impossible to determine just how much of an impact the campaign had on German operations and subsequent Allied sinkings, the fact remains that the airplane was proving itself to be a formidable anti-submarine platform. Some of the search-and-attack tactics devised and implemented on the Spider Web are practiced by navies around the world today. The greatest impact of the fixed-wing aircraft in the RNAS during World War I, however, was realized in support of the convoy system. 1 Ibid. 2 2 Ibid. 8 3 Ibid Ibid Ibid Ibid Ibid Ibid Ibid Halpern, 441 Notes 18

26 Chapter 7 The Impact of the Flying Boats on the Convoy System With the increasing effectiveness of the barrage in the Dover Straights in the last 18 months of the war, the flying boat squadrons in Southeastern England began to discover fewer targets in the waters covered by the Spider Web. To keep flying skills sharpened, the RNAS began integrating the flying boats into the convoy system. Initially, coordination between destroyers, cruisers and flying boats was difficult as there were no procedures for integrating aircraft into convoy operations. The U-boats, it was discovered, typically conducted torpedo attacks on single merchant ships from a range of yards while submerged in front of their prey. To attack a convoy, however, the U-boats positioned themselves yards in front of the convoy and shot a torpedo not at a particular ship, but at the cluster of vessels. 1 Critical to the success of a torpedo attack, was the U-boat s ability to place itself in front of the convoy. To accomplish this, a U-boat had to surface to discover the convoy in the first place, determine its course and speed, and then position itself in an optimal firing position. The weakness of having to surface to determine the location of a convoy was exploited with great effectiveness by the flying boats. The day prior to the departure of an escorted convoy, flying boats were assigned to patrol the intended route in order to cleanse it of enemy submarines. This had the 19

27 effect of driving the U-boats to submerge and denied them the opportunity to charge their batteries in anticipation of an attack. The following day, when the convoy sortied, flying boats continued to patrol the waters ten nautical miles in front of the convoy. This further limited a U-boat s ability to maneuver to a perfect firing position as again, it was forced to submerge, cutting its speed in half and rapidly depleting its batteries. 2 The flying boats were limited to three hours on station so several shifts were flown to provide unbroken air cover along the entire route through dangerous waters. Once the Royal Navy finally settled upon a convoy strategy, and combined it with the technologies and other supporting strategies previously discussed, the effectiveness of the U-boat steadily degraded. From April, 1917 through October 1918, the British provided escort protection for 83,958 individual ship sorties in all operational waters. From those sorties, 257 ships were sunk due to U-boat attack for a loss rate of only 0.31%. 3 The convoy system had proven to be very effective at removing the effectiveness of the U-boats without actually destroying them in significant numbers. Of even greater interest however, is the effectiveness of the flying boats in support of the convoy system. Within the numerous convoys that were escorted by surface combatants in combination with flying boat assets, a grand total of only two ships were lost during the entire period of their employment. 4 The contributions of RNAS fixed-wing aircraft to the ASW campaign of World War I are difficult to quantify. While several sightings and attacks were made by the flying boats operating on the Spider Web, the actual number of kills made by aircraft remains unknown. What is certain is that the airplane was very effective at harassing the U-boats and forcing them to submerge, thereby limiting their capabilities. Aircraft- 20

28 protected convoys were virtually immune to U-boat attack. 5 The lessons learned and the capabilities demonstrated by the RNAS in the U-boat campaigns of World War I provided a foundation for airborne anti-submarine warfare which would last into the twenty-first century. The Royal Navy combined several capabilities to detect, localize, track, and defeat German submarines. No single tactic or weapon single handedly defeated the U- boats, but rather it was a combination of various techniques and evolving strategies. Some strategies were quickly embraced, the armed Q-ship for example, while others were resisted, like the convoy system. The Royal Navy combined the use of mine warfare, barrages, hydrophones, wireless radio listening stations, Q-ships, zigzag course patterns, escorted convoys, spider web surface search grids and airborne convoy escorts in an allout effort to defeat the U-boats. That victory was eventually gained, not by destroying the German submarines, but by rendering them ineffective. The ASW tactics, techniques and procedures practiced today trace their roots to the Royal Navy of World War I. Notes 1 Hallam, 80 2 Ibid The World War I Document Archive August, 1995, on-line, Internet, available from 4 Ibid. 5 Halpern,

29 Chapter 8 United States Navy Anti-submarine Warfare Pre 1999 It should come as no surprise that the United States Navy and other navies of the world have studied and incorporated the lessons learned from the Allied ASW campaign of World War I. Like the Royal Navy from , the United States Navy does not rely on any single tactic or platform, but rather combines multiple capabilities from various assets in an integrated effort to detect, classify, track and possibly attack enemy submarines. The height of this anti-submarine effort was reached during the Cold War when submarines from the Soviet Union regularly patrolled every ocean of the world. To detect the presence of submarines in the First World War, the Royal Navy relied heavily on visual contact from surface craft, kite balloons, and aircraft. Eventually the RN incorporated the use of acoustic technology in the form of crude hydrophones. The electronic spectrum was also exploited through the use of wireless listening stations. All these detection capabilities worked together to notify British commanders of enemy submarine presence. In addition to these specific detection techniques developed by the British, the United States would adopt technologies which would incorporate space power. Space power would be used to enhance visual detection in the form of satellite imagery of submarine departures from Soviet Naval bases. 22

30 Acoustic detection capabilities were greatly increased by improving upon the British hydrophone model and placing hydrophones on submarines and surface combatants in the form of bow-mounted sonar domes and towed-array sonar. Furthermore, acoustic technology was developed for use by aircraft in the form of sonobuoys and dipping sonar. 1 Finally, combining the principles of a World War I barrage and acoustic technology, permanent detection hydrophones were placed along underwater choke points transited by Soviet submarines in the North Atlantic and Pacific which alerted US Naval commanders of Soviet activity. The use of the electronic spectrum to detect submarines was greatly enhanced by improvements in electronic surveillance measures (ESM). Building upon the concept of wireless listening outposts developed by the British, the US Navy placed ESM equipment on surface ships, submarines and aircraft which are capable of working in unison to triangulate an accurate wireless fix of an enemy submarine s position. Furthermore, the invention of Radio Detection and Ranging (RADAR), and specifically Inverse Synthetic Aperture Radar (ISAR) 2, greatly enhanced the use of the electronic spectrum to detect submarines. Even the earth s magnetic field has been exploited for the purposes of submarine detection, and more specifically, position fixation. Submarines create local anomalies in the magnetic field as they transit the oceans. Naval aircraft have been equipped with Magnetic Anomaly Detection (MAD) equipment which alerts aircrews to a submarine s presence when the aircraft flies directly over a submarine, thereby not only detecting it, but accurately fixing its position. 23

31 All of these technologies, exploiting the physics of the electronic, magnetic, acoustic and visual spectrums have been incorporated, to the maximum extent possible, by naval and national assets in the subsurface, surface, airborne and space mediums. Working in unison, they have created formidable anti-submarine warfare capabilities. The parallels between ASW practiced by the British in World War I and today s navies are not limited to the improvement and incorporation of ASW technologies. The United States and Allied Navies have also revised and implemented World War I British ASW tactics. Unable to actively hunt and destroy Soviet Submarines without sparking World War III, the US Navy followed the British lead by devising tactics to minimize the effectiveness of Soviet submarines. Although merchant convoy operations have not been practiced by the United States since World War II, US Navy Carrier Battle Groups and Amphibious Battle Groups, like the merchant convoys, were often followed by Russian submarines during the Cold War. To minimize the impact of these submarines, the US Navy employed surface craft, submarines and more specifically, aircraft to cleanse the waters along the intended course of the respective battle groups. This had the same effect on the Russian submarines that it had on the U-boats. Unable to approach US battle groups to the desired range, Russian submarines could neither launch torpedoes nor surface-to-surface anti-ship missiles. They were effectively defeated through mission denial. Current airborne ASW tactics trace their roots to the RNAS flying boat squadrons. The generation of a rough submarine position based on wireless cross-fixing resulted in the launching of a flying boat to the Spider Web search grid. Today, based on submarine contact generated from any of the myriad of detection capabilities previously 24

32 discussed, US Naval aircraft standing ASW alert launch to specific ocean search sectors containing the suspected enemy submarine. Even airborne ASW attack principles follow the standard established by the RN in World War I. Reminiscent of the flying boat squadrons, US Naval aircraft, given the order, would attack an enemy submarine by approaching from the stern, at low altitude, and dropping a torpedo on the submarines estimated position. In the interest of developing platforms which build upon the World War I model, and combine as much of this technology and tactical capability as possible, the United States Navy developed and purchased the S-3B Viking carrier- based jet aircraft during the 1960s and 1970s. Designed specifically as an anti-submarine asset, the Viking combined acoustic technology in the form of sonobuoys, with MAD equipment, ISAR for periscope detection, electronic surveillance equipment and infrared visual enhancement all to detect and track Soviet submarines. In addition to all this detection capability, these eyes in the sky also had teeth. The S-3B was capable of carrying up to four Mk-46 anti-submarine torpedoes. Finally, the S-3B, or War Hoover as she is known by her crews, had the capability to remain airborne for up to seven hours without in-flight refueling; a capability that allowed the searching of extensive amounts of water space. 3 The combination of detection capabilities and firepower provided battle group commanders a formidable ASW weapon in the S-3B Viking. Notes 1 Dipping Sonar is a detection technique whereby a helicopter lowers a hydrophone while in a hover configuration. The hydrophone generates sonar contact with a submarine and can determine the range and bearing from the helicopter. 2 ISAR RADAR is a version of RADAR that can not only detect the presence of a ship, but is capable of classifying the type of ship and is especially adept at detecting a submarine periscope. 25

33 Notes 3 Naval Aviation Training and Operations Procedures Standardization, S-3B Flight Manual, (San Diego, CA.: Naval Printing Office, 1998), Chap 2 26

34 Chapter 9 Degrading Anti-Submarine Capabilities with the Demise of the U.S.S.R. With the fall of the Berlin Wall in 1989 and subsequent dissolution of the U.S.S.R. the following year, the United States noted fewer and fewer submarine sorties being conducted by the former Soviet submarine fleet. The United States Navy began to find itself in the unfamiliar position of having to defend expenditures on ASW assets against members of Congress who were clamoring for a Peace Dividend. Near the end of the millennium, the US Navy began to trim its arsenal of fixedwing ASW assets by de-funding the ASW mission performed by its carrier-based Vikings. Starting in 1997, the S-3B squadrons had their aircrews reduced in number by 25%. Furthermore, all acoustic computer hardware as well as software programs were removed from the aircraft. Viking anti-submarine training ceased in both training and operational squadrons. Looking to gain additional cost savings, the US Navy decided to retire the S-3B fleet altogether between the years As of the writing of this paper, two of ten Viking squadrons have already been decommissioned with an additional two set to retire during While the United States Navy still maintains its fleet of P-3C shore-based ASW aircraft, it effectively stripped its carrier strike groups of their only fixed-wing, organic 27

35 ASW asset. The ramifications of this decision are far reaching. The P-3C is an effective submarine hunter, but is limited by shore-basing requirements and struggles to integrate into carrier operations. By retiring the Vikings, the US Navy carrier strike groups (CSG) no longer have an on-board RADAR system designed to detect periscopes in waters beyond submarine launched surface-to-surface missile range. Other fleet surface RADAR systems only detect a contact, with no ability to discern between a merchant vessel and an 18-inch periscope. The CSGs have lost the ability to drop up to 60 sonobuoys and multiple torpedoes on an enemy submarine from a single asset. Several helicopters would be forced to launch to drop a comparable number of sensors and weapons. Additionally, the CSGs no longer have the ability to send out long-range, fixedwing aircraft to sweep projected carrier transit waters up to 300 nautical miles in front of the strike group. In order to cleanse an equivalent water space, CSG commanders are forced to disperse submarines, destroyers, cruisers and frigates in an expensive effort to perform the work originally accomplished by a crew of four on a single aircraft. Finally, and perhaps most critically, with the retirement of the Vikings, the US Navy is steadily losing personnel with the combined corporate knowledge of carrier operations and airborne ASW tactics. Viking aircrews are either retiring from service or being absorbed by other naval aviation communities. A critical portion of the art of ASW is being forgotten. The ship-based ASW replacement to the S-3B Viking is an aging fleet of 28

36 SH-60B/SH-60F Seahawk helicopters. Like the P-3C, the Seahawks are excellent submarine hunters and unlike the P-3C, are not limited by shore basing constraints. The Seahawks are capable of deploying from smaller combatant ships; a capability that provides them multiple landing pads throughout a CSG. The helicopters, however, have inherent disadvantages which do not exist with the S-3B Vikings. The detection, localization, fixing and tracking of a submarine is a timeconsuming business, often requiring aircraft to remain on station for several hours. The primary disadvantage of using helicopters for the ASW mission lies in their range and speed limitations. In order for a fully-fueled, ASW-loaded helicopter to be effective for any significant amount of time, it must limit itself to a 50-nautical-mile range. The Vikings provided the same services at ranges up to 300 nautical miles. Furthermore, aircraft on ASW alert must be able to pounce quickly on newly detected submarine positions and helicopters simply do not have the speed of a twin-engine jet like the Viking. The second disadvantage of using the Seahawks for airborne ASW lies in the fact that they were designed as multi-mission platforms. In addition to the ASW mission, the Seahawks have anti-shipping, special operations, combat search and rescue, and logistics missions, making them a kind of jack of all trades and master of none. Training time and resources dedicated to the ASW mission are constrained by the Seahawks other multi-mission roles. Furthermore, to fulfill its multiple missions, the Seahawk requires multiple on-board systems. The plurality of these systems necessitates a more generic design in order to reduce weight. Included in the generic equipment is the ASW suite. For example, none of the Seahawks have the periscope-sensitive ISAR RADAR and a 29

37 majority have no MAD equipment on board. The Vikings were designed specifically for the ASW mission and were dedicated solely to that mission during their first decade of existence. Finally, the Seahawk helicopters do not have the weapon and sonobuoy-carrying capacity of the retiring Vikings; a fact that effectively requires the launching of multiple helicopters to accomplish the same mission. The launching of more aircraft is a viable option, except for the fact that US Navy CSGs deploy with fewer ASW helicopters than they did S-3B Vikings. With the retirement of the Vikings, CSGs are deploying with more land strike aircraft, while the population of ASW helicopter assets has remained the same. 30

38 Chapter 10 Gathering Threats Proponents of the decommissioning of the S-3B Vikings, without a suitable fixedwing replacement, have argued that the submarine threat to the United States has steadily diminished with the downfall of the Soviet Union. To some extent, from a high seas standpoint, they are correct. There is not a belligerent nation in the world sending submarines to harass US Navy Carrier Strike Groups or Expeditionary Strike Groups on the high seas. Unfortunately for US and Allied navies, the high seas are not the focus of gathering threats. Belligerent nations, specifically Iran, China and North Korea, have focused their naval strategies in the littoral, or brown-water oceans immediately surrounding coastlines. These strategies are reminiscent of the U-boat campaigns in British waters between 1914 and Iran, a state sponsor of terrorism and a dedicated enemy of the United States, currently owns three Russian-built Kilo class diesel-electric submarines with a fourth slated to join the inventory in the near future. 1 Like the U-boats operating in British waters during World War I, these submarines operate in Iranian coastal waters within the Persian Gulf and the Gulf of Oman and have tremendous potential to wreak havoc on world oil shipments as well as supply routes supporting OPERATION IRAQI FREEDOM. These diesel-electric submarines practice the same tactics as the German U-boats in that 31

39 they surface to acquire a fix on enemy shipping and must stay surfaced to charge batteries. Unlike the German U-boats, however, the Iranian Kilos are capable of acoustically fixing and attacking their targets while remaining submerged. Furthermore, the Iranian Navy has observed US Naval operations in the Persian Gulf for 15 years. The Iranians are familiar with carrier zones, combatant patrol areas, and rotation schedules. The Iranian Navy, and in particular its submarines, presents a serious threat to US Naval interests in the region. North Korea is among the belligerent countries with a dedicated hatred for the United States and has an active littoral submarine building program. The North Korean navy currently employs 29 diesel-electric submarines of various classes that are capable of operating beyond the littoral waters of its coastline, and 22 submarines exclusively dedicated to coastal waters. 2 Like the Iranians, the North Koreans have had the opportunity to quietly watch the Seventh Fleet of the US Navy, based in Japan, conduct operations over the course of decades. As in the Persian Gulf, the Pacific waters surrounding the Korean Peninsula, China and Japan are some of the busiest shipping waters in the world. The North Koreans have the added advantage of the United States being focused on operations in the Middle East. The S-3B Vikings currently stationed in Japan are set to be retired by October, Finally, and perhaps most importantly, the Chinese Navy, like its Iranian and North Korean counterparts, incorporates the use of nine diesel-electric submarines in its coastal waters. Additionally however, the Chinese Navy owns one nuclear-powered ballistic missile submarine with a second one planned for completion in the next two 32

40 years. 3 Tensions between the United States and China could increase at any time over issues concerning Taiwan or North Korea. All of these nations have at least a suspicion of the United States, if not an outright hatred. All three sit astride the world s busiest trade routes. All three have employed World War I U-boat technologies and tactics in the development of their submarine forces. Finally, these countries are growing increasingly proficient in submarine operations making them more difficult to detect and track. They have the capability and the motive to use their submarine forces in a confrontation with the United States Navy and are actively seeking additional capability. In short, submarine threats are gathering while the United States reduces ASW capabilities. Notes 1 Jane s Fighting ships (Alexandria, VA.: Jane s Information Group, 2005), Ibid Ibid