Coastal Command

On this day in 1945, 4 June, Coastal Command ended the longest war campaign of any RAF Command. Coastal Command (‘CC’) arguably failed to receive the attention and recognition it deserved for its crucial role in keeping open Britain’s sea lanes from the world; a 24-hour mission across an empty ocean is less glamorous than dropping a bomb on Berlin. But was arguably more important.

It is difficult to be precise about when the very first ‘offensive’ patrol was undertaken. Air Commodore Graham Pitchfork writes in ‘RAF Day by Day’ that the first war action is noted as having taken place 24 August 1939, when 48 Squadron’s Avro Ansons started patrols over the North Sea – 10 days before Britain declared war and, indeed, 8 days before the German invasion of Poland, which started the war. But 48 Squadron’s Operations Record Book states, for example, that on 11 February 1939 it was tasked with locating a German tanker and submarine and on 20 March it located and photographed the German fleet in the North Sea.

Sunderland concludes last-ever war mission. Note additional fixed machine guns under nose turret. (Crown copyright. Ministry of Defence CH 15302)

After taking off from the Northern Irish base at 1643 hours on 3 June, the aircraft set course to intercept convoy HX358 which consisted of 51 vessels, locating them at 2121 hours. The aircraft remained on station until midnight when the order “CEASE PATROL!” was received, and alighted on Lough Erne at 0321 hours to end Coastal Command’s operational effort during the Battle of ther Atlantic.

The last war patrol ended at 0001 hrs. on 4 June 1945, 27 days after the German forces had formally surrendered. Although Grandadmiral Karl Dönitz, (whom Hitler nominated as German President before his suicide) had ordered all U-Boats to surrender, by surfacing and displaying a large black flag, the Royal Navy and CC were taking no chances; some U-Boats might genuinely not receive the order but there was also the fear that some might refuse to comply. This very last European combat flight was operated by Short Sunderland serial ML 778, coded NS.Z, (Captain, Wing Commander J Barrett) from No. 201 Squadron RAF, based at Castle Archdale, County Fermanagh.

Coastal Command Resources

In September 1939, all RAF resources (and indeed Naval and army) were wholly inadequate to the challenges ahead, but none more so than Coastal Command. Their primary task was the patrolling of inshore waters and protection of convoys: merchant shipping was placed under Admiralty control on 26 August 1939, and the first convoy sailed on 2 September.

The available aircraft were woefully inadequate in both numbers and capability. On 1 September, Coastal Command’s Order of Battle listed 14 squadrons at 15 British bases and the following front-line aircraft:

• Avro Anson 301
• Lockheed Hudson 53
• Vickers Vildebeest 30
• Short Sunderland 27
• Saro London 17
• Supermarine Stranraer 9

But the Order of Battle also shows only 163 actually serviceable.

Supermarine Stranraer (RAF Museum P014425)

The Submarine Threat

The only thing that really frightened me was the U-boat peril.
Prime Minister Winston Churchill in his memoirs

The aeroplane can no more eliminate the submarine
than the crow can fight a mole.
Admiral Karl Dönitz, Commander U-Boats, August 1942

Britain is a small, densely populated, island wholly dependent on maritime trade to import the food and raw materials needed by a complex industrial economy, especially its war industries. During the Great War [First World War], German submarines (U-Boats from the German Unterseeboot) had a policy of unrestricted attacks on shipping, Allied and neutral – a ‘sink on sight’ policy – which in 1916-17 came very close to starving Britain into surrender. The Admiralty fully expected a repeat, should war break out in 1939, a belief made real.

Britain declared war on Germany at 11.00 on 3 September 1939; just 8 hours and 39 minutes later, the liner SS Athenia was torpedoed off the Irish coast with major loss of life (passengers and crew). So the U-Boats were already out there and waiting. And during the dark days of 1942-43, they came close to achieving what they had failed to do in 1917. U-Boats were sinking Allied merchant ships faster than shipyards could replace them: the blackest month was May 1943, with sinkings of 120 ships totalling 693,000 tons.

Just as in the night skies over Germany, CC’s war was as much technological and electronic as Bomber Command’s: a constant leap-frogging of offence and defence. From 1939 to mid 1943, U-boats were in the ascendant; CC dominated from then until early 1945 when the Kriegsmarine introduced a new technology which revolutionised submarine warfare.

During the war, and perhaps even today, most people measured the success of Coastal Command by the number of submarines destroyed: but that was based upon a false assumption – that destroying the boats was the most important activity. In fact, as stated in the ‘Western Approaches Tactical Policy’, issued in April 1943 by Admiral Max Horton, Commander-in-Chief of Western Approaches, the primary military objective for both Royal Navy and Royal Air Force was ‘the safe and timely arrival of the convoy’.

Submarine Technology

Today’s nuclear-powered submarines – uncomfortable and cramped as they unarguably are – represent a far, far cry from those used in by both sides in the Second World War. Today, the boats [submarines are traditionally called ‘boats’] are fast and can remain submerged for literally months. Top speed of a nuclear boat is highly classified but even in the 1970s, speeds in excess of 35 knots (40 mph, 64 kph) were published. And the Royal Navy has just [May 2025] set a record with a Vanguard class Trident missile-carrying boat remaining submerged for 204 days without once breaking surface.

By contrast, submarines of the war could proceed on the surface at the speed of a man bicycling but under water, barely at walking pace. And they relied on massive batteries driving electric motors for under-water propulsion, batteries which needed charging every 24 hours by surfacing and generating electricity from the diesel engines used for surface propulsion.

Submerging for much longer than 24 hours risked killing the entire crew from oxygen starvation or carbon monoxide poisoning in a boat whose batteries were exhausted. Until a German invention which radically tilted the scales back in favour of the submarine: the Schnorchel – a pipe raised above the surface drawing in air and discharging exhaust fumes, enabling a submarine to recharge its batteries whilst remaining submerged and travelling underwater at close to the same speed as on the surface.

The radar of the time could not detect a Schnorchel so the boats had again become invisible. Fortunately, by the time this technology could be produced at scale, Allied armies were moving into Germany and the war was nearly over: had this technology been widely deployed in 1943, the war might have ended very differently.

Submarine Tactics

Admiral Dönitz, overall U-Boat fleet commander, developed a strategy to form his U-Boats into Wolf Packs, a concentration of boats around a single convoy at a time. This involved setting a line of U-Boats across a convoy route with the first to spot it shadowing the convoy and calling in reinforcements by wireless, aided sometimes by reconnaissance flights by a Focke Wulf Fw 200 Condor/Kurier land-based aircraft. But given its very limited underwater speed, a shadowing submarine had to remain on the surface so if forced to dive by any aircraft circling the convoy, even if the aircraft did not spot the submarine, it could not match the convoy’s speed, thus allowing the convoy to escape. On that basis, even unarmed Tiger Moths patrolled the North Sea in the Autumn and Winter of 1939.

How to find a submarine

How do you find a U-Boat, a tiny speck in a vast ocean?

Initially, the Mk. 1 Eyeball and a pair of Zeiss binoculars. Not much good by day and useless by night. Then introduce ASV [Anti Surface Vessel] radar. In daylight, accurate enough to find the target visually, again not much use by night as insufficiently accurate for an attack. Then add a Leigh Light – a massive searchlight on the aircraft. Find the submarine by radar then, when a mile or so away, point the searchlight at the radar target, switch on and hopefully a very startled U-Boat is seen on the surface, charging its batteries.

Consolidated Catalina 210 Squadron.
Note Leigh Light under starboard wing and radar aerials on both aircraft (RAF Museum P 011892)

Once underwater, one can only roughly estimate its position. Surface warships were equipped with ASDIC. This device – derived from the acronym for Anti Submarine Detection Investigation Committee and now called Sonar – was in effect underwater radar using sound rather than electric pulses – the ‘pings’ heard on war films when hunting submarines. But the ASDIC transmitter and receiver both had to be under water so a new device, a sonobuoy, was developed.

Dropped by an aircraft, it too located the U-Boat by sound and transmitted its position back to the circling aircraft. A final device introduced on a very limited basis was MAD – Magnetic Anomaly Detection. The metal hull of the boat slightly distorted the Earth’s natural magnetic fields, a distortion which can be measured. United States Navy Catalinas operating under CC command at Gibraltar are known to have used MAD but this author has not seen any references to RAF aircraft being so equipped.

Leigh Light. This one retracts into belly of Wellington aft of bomb bay.
(RAF Museum London)

Other electronics also helped detect the U-Boats, which had to send sighting reports back to headquarters in Lorient, France, when shadowing a convoy, as well as routine weather and fuel reports. To which Allied ships and aircraft were listening and by taking cross bearings using ‘Huff Duff’ [High Frequency aerials], could locate the boats.

At the same time, Kriegsmarine headquarters were transmitting orders to the U-Boats which were intercepted and decrypted by Bletchley Park, so CC knew where the Wolf Pack would be assembling and hence define the search area more tightly. This decryption was aided in no small measure by the Royal Navy having captured a U-Boat in May 1941 and seized its crucial Enigma machine and related code books.

Attack Methods and Weapons

Given the importance of aircraft over a convoy, the critical performance criterion of an anti-submarine aircraft was range. The North Atlantic is vast: a typical convoy route from Liverpool to Halifax, Nova Scotia, had to cover 2,500 nautical miles.

The best that CC had in 1939 was the Sunderland with a nominal range of 1,000 miles but that allowed no margin for weather nor time over the convoy. CC began to re-equip with modified bomber types (Whitley, Wellington, Halifax, occasional Fortress but never Lancasters, all much to the chagrin of Air Marshal Harris, who wanted every bomber built to be given to Bomber Command to destroy the German cities where submarines were constructed) but even after CC bases were established in Northern Ireland, Shetland Islands, Iceland, Faroes, Azores and Ascension, and including RCAF from Nova Scotia, Labrador and latterly Greenland, there was still a ‘Mid Atlantic Gap’ where U-Boats could lurk, safe, unless the convoy was important enough to be allotted an RN escort carrier or MAC (Merchant Aircraft Carrier).

Mid Atlantic Gap – beyond air cover
(RAF 1939 – 1945 Official History Vol. 2 ‘The Fight Avails’ – see Bibliography)

The Gap was finally closed by two excellent products of the Consolidated Aircraft Corporation: the VLR [Very Long Range] Liberator and Catalina, the former with a range of up to 2,400 miles and the latter, capable of flying for 27 hours, a range of 2,500 miles. Patrols of up to 24 hours appear to have been routine.

Operations Room wall plot at Headquarters Coastal Command RAF Northwood
(RAF Museum AL00170)

Having located a U-Boat, how to destroy it?

During the Second World War, the primary air-launched anti-submarine weapon was the depth charge. Exploding under water, if near enough to the submarine (preferably within 50 yards), the shock wave would cause major internal damage and start leaks, even if it did not rupture the submarine’s pressure hull. But to be effective, the attacking aircraft should ideally fly at 450 to the submarine’s track, and at low level for accuracy, to achieve a “straddle” – depth charges dropped each side of the boat.

As the war progressed, a more effective air-launched weapon was the homing torpedo. This tracked the sounds caused by the boats’ propeller cavitating in the water – and a submarine cannot stop moving underwater or it would lose control over depth.

Sunderland depth charges (RAF Museum London)

The Magnetic Anomaly Detector created more technical problems. A conventional bomb sight looks forward but the MAD can only say when it is directly over the submarine: any weapon dropped at that point would describe an arc down to the water, the impact distance ahead of the release point being in tens or hundreds of yards depending upon the speed and altitude at which launched.

So a new device was invented – the reverse-firing bomb. At the moment of maximum MAD signal, the weapons would fire backwards at exactly the forward speed of the aircraft so would fall vertically. One of many electronic and technological advances during the latter half of the conflict.

Contemporary Ministry of Information propaganda/recruiting poster
highlighting surrender of U-570 to Coastal Command Hudson 27 August 1941
(RAF Museum FA 11020)

An unique event occurred on 27 August 1941: the sole example of a submarine surrendering to an aircraft without the intervention of surface vessels. Hudsons from 269 Squadron were on patrol off Iceland when they spotted U-570 surfacing due to mechanical problems and with an inexperienced crew.

Aircraft dropped depth charges, causing the crew to fear the damage had caused battery leaks and deadly chlorine gas being caused by the reaction with sea water, so they surrendered by waving white cloths. The Hudson pilot ceased fire and called for reinforcements.

More aircraft arrived, including another Hudson and a Catalina from 209 Squadron, which had sunk U-452 just two days earlier. Despite U-570’s radio call for help, the swarm of RAF aircraft kept other U-boats at bay until an armed trawler arrived that evening to take possession of the submarine.

Submarines Fight Back

In the early years, a U-Boat would submerge as soon as an aircraft was sighted. But the Kriegsmarine realised how vulnerable the attacking aircraft were as they flew low (and slow) on their attack run so started mounting extensive anti-aircraft guns on the submarine, more powerful and longer-ranged than the modest aircraft armament. And the U-Boats began fighting back! Instead of diving when attacked, they would stay on the surface and fight.

Type VIIC submarine U-361 under attack by Flight Lieutenant John Cruickshank; for sinking this he was awarded the Victoria Cross. Note splashes from aircraft machine guns and two twin flak mountings on conning tower. (RAF Museum X004-7598/11)

CC responded in two ways: improving aircraft armament; and developing ‘stand-off’ weapons. The Sunderland had only a nose turret with two 0.303 machine guns to fire against the U-Boat it was attacking whereas some U-Boats had multiple 20 mm cannon and even a 37 mm cannon to fire against an attacking aircraft. And early Liberators had no nose turret and just one 0.5 inch machine gun. So Sunderlands were fitted with an additional four fixed 0.303 machine guns whilst some Liberators had belly pods with four 20 mm cannon.

Beaufighters, Mosquitoes and even Liberators had 8 Rocket Projectiles capable of penetrating the boats’ pressure hulls; on Liberators, they were on stub fittings below the cockpit.

VLR Liberator. Note Rocket Projectiles rack below cockpit (RAF Museum AR P011963)

A limited number of Mosquitoes were even fitted with a Molins gun, a modified 3.7 inch (57 mm) army weapon also capable of breaking through a submarine’s pressure hull or hull of a merchant ship.

Molins 6 pdr. Class M gun (RAF Museum London)

But as CC became bigger and better equipped, they wanted to go onto the offensive and prevent the U-Boats getting anywhere near a convoy, so they patrolled the Bay of Biscay, which U-Boats had to transit from their French bases to the deep Atlantic. The Germans retaliated by providing fighter escorts for the boats by Ju 88 twin-engined, highly effective fighters. So, in turn, the Liberators and Catalinas over the Bay of Biscay would have Beaufighter or Mosquito escorts.

Pigeons join crew – carried to send position report home after ditching.
(RAF Museum AL00235)

Balance Sheet

On 7 May 1945, the last U-boat to be sunk by an aircraft under RAF Coastal Command control, Type VIIC submarine U-320, was attacked by a Catalina of No.210 Squadron flown by Flight Lieutenant K.M. Murray. The submarine subsequently sank on 9 May off the Norwegian coast – none of the crew survived.

Two files in The National Archives give an absolute wealth of statistics regarding Coastal Command’s equipment and activities: ‘Coastal Command War Statistics’ (AIR 15/685); and ‘Coastal Command Orders of Battle January 1944 to December 1947’ (AIR 15/703), of which the following is only the briefest of summaries.

The Order of Battle for 6 June 1945 listed 13 UK bases plus Gibraltar, Azores and Iceland. And by now, others such as Dakar in West Africa, had already closed. CC aircraft were also operating in the India/Burma theatres but are counted under SEAC returns.

Altogether, 23 basic types of aircraft were used (disregarding Mark number and ‘owner’ variants – such as Bomber Command, Fleet Air Arm, USAAF and USN operating under CC control).

On 8 May 1945, total CC aircraft strength was 1,115, of which front-line maritime patrol, were:

• Catalina/Canso 45
• Halifax 27
• Liberator 225
• Sunderland 78
• Wellington/Warwick 155

Admiral Dönitz had been proven very wrong: the crows had pecked long and hard. Between 3 September 1939 and 8 May 1945, Royal Air Force, United States Army Air Force and United States Navy aircraft, all under RAF Coastal Command control, had destroyed 288 by aircraft alone, and a further 47 involving aircraft and surface warships.

Around 120 aircraft were shot down by U-boats for the loss of roughly 30 U-boats either sunk during the attack or due to being located by other forces shortly afterwards and sunk. By the cruel and harsh statistics of war, that was a good result. Losses of life would have been roughly similar but a U-Boat demanded huge manufacturing resources and raw materials, taking long times to build. Whereas Henry Ford’s aircraft factory at Willow Run, Detroit, (the largest building in the world at that time) turned out one Liberator every 56 minutes.

A total of 5,866 aircrew and 2,166 aircraft were lost on all CC operations whilst flying 238,300 sorties lasting 1,314,324 hours. Total personnel (RAF, WAAF, RAAF, RCAF, RNZAF and including refugee volunteers from Occupied Countries) rose from 11,600 on 1 January 1940 to 30,300 in July 1945.

Coastal Command aircrew won four Victoria Crosses, three of them against U-Boats:

• 6 April 1941 Flying Officer Kenneth Campbell RAF (posthumous) (Beaufort)
• 11 August 1943 Flying Officer Lloyd Trigg RNZAF (posthumous) (Liberator)
• 24 June 1944 Flight Lieutenant David Hornell RCAF (posthumous) (Canso)
• 17 July 1944 Flight Lieutenant John Cruickshank RAF (Catalina)

Coastal Command is well represented in RAF Museum London: Short Sunderland, Bristol Beaufort, Bristol Beaufighter, Lockheed Hudson, Fairey Battle, Molins gun and Leigh Light.

A Blog of some 3,000 words cannot begin even to scratch the surface of summaries of the longest campaign which was cruel and bloody and the most vital to Britain’s survival and ultimate victory; fought by many brave men on all sides: Royal Navy, Royal Air Force, Merchant Navy and other Allied forces. But not excluding the U-Boat crews who may have been fighting for an evil regime but they endured appalling losses – up to 70% killed – but still continued volunteering to the very end. This author encourages interested readers to undertake their own research and the following is a short summary of a few of the very many sources available.

BIBLIOGRAPHY AND FURTHER READING

• Coastal Command Review 1942-1945: a monthly digest of activities RAF Museum PR06052 – PR06058 [Author: classified Secret but written in popular magazine style]
• Royal Air Force 1939-45, Official History in 3 volumes. Denis Richards and Hilary St G: HMSO 1953 Hardback and 1974 paperback (Available to study in the Museum’s Reading Room at Hendon.)
• Aircraft versus Submarine, Alfred Price: William Kimber 1973
• The U-Boat Hunters, Anthony Watts: Macdonald and Jane’s 1976

[The above four sources are highly recommended by author]

• Coastal Command at War, Chaz Bowyer: Ian Allan 1979
• Coastal Command 1939-45 Photographs from the Imperial War Museum Ian Carter: Ian Allan 2004
• Coastal Command in Action Photographs from the Public Record Office [now The National Archives] Roy Conyers Nesbit: Sutton Publishing 1997
• Coastal Command 1939-1942 HMSO [wartime publicity book]
• TNA AIR 15/99 Photos of a German submarine surrendering to the RAF Nos. 209 and 269 Squadrons (Reykjavik) 27th August 1941
• TNA AIR 15/333 Coastal Command Order of Battle (Weekly) with location maps 5-2-43 – 14-6-43
• AIR 15/685 Coastal Command War Statistics
• AIR 15/702 Orders of Battle 1 July 1939 – 31 December 1943
• AIR 15/703 Orders of Battle 1944-47
• AIR 15/758 Coastal Command monthly summary of operations 1 October 1939 – 30 September 1941
• AIR 27/469/1 Operations Record Book 48 Squadron 1 November 1935 – 30 September 1939 PDF
• AIR 27/1179/36 Operations Record Book 201 Squadron June 1945