'Musketry' was a British programme of RAF and Fleet Air Arm aircraft patrols over the Bay of Biscay, in concert with the 'Seaslug' naval patrols, designed to find and destroy U-boats running on the surface while on transit to or from their hunting areas in the Atlantic (1 July/2 August 1943).

From 1 July, aircraft of RAF Coastal Command’s No. 19 Group begin 'Musketry'. Three times a day, seven aircraft flew parallel courses after reaching an area off Cape Finisterre in neutral Spain. When a U-boat was sighted and reported, the aircraft then converged and attacked as a pack. The tactic proved to be very effective, and involved Consolidated Liberator aircraft of the British Nos 53, 86 and 224 Squadrons plus similar B-24 aircraft of the USAAF’s 1^st and 4^th Anti-Submarine Squadrons, Consolidated Catalina flying boats of the British No. 210 Squadron and similar PBY-5A boats of the US Navy’s VP-63 Squadron fitted with MAD (magnetic anomaly detector) equipment, Short Sunderland flying boats of the British Nos 226 and 228 Squadrons and Australian Nos 10 and 461 Squadrons, Vickers Wellington aircraft of the British Nos 172 and 547 Squadrons, the Canadian No. 426 Squadron with Leigh Light equipment, the Free Polish No. 304 Squadron and the Czechoslovak No. 311 Squadron, Boeing Fortress aircraft of the British No. 59 Squadron, and Handley Page Halifax aircraft of the British Nos 58 and 502 Squadrons.

Initially, the naval force comprised the escort carrier Archer, light cruisers Bermuda and Glasgow, and the lighter warships of several escort and support groups, most notably Escort Group B2 and the 2^nd Support Group. These British joint air/sea operations over and in the Bay of Biscay, off the western coast of German-occupied France, were a special effort at the height of the Battle of the Atlantic, and during the period 13 U-boats were lost to Allied air attack in the Bay of Biscay.

The effort was part of the British response to the new German tactic, from the beginning of June, for U-boats to make their transit of the Bay of Biscay in groups of two to five boats in order to be able to support each other with anti-aircraft fire in the event that the group came under air attack. The Junkers Ju 88C heavy fighters of the I/Zerstörergeschwader 1 also provided fighter protection in the inner part of the Bay of Biscay even though these aircraft were significantly inferior to the British Beaufighter heavy fighters of the RAF�s No. 248 Squadron and the de Havilland Mosquito heavy fighters of Air Vice Marshal C. R. Steele’s No. 10 Group of Air Marshal Sir Trafford Leigh-Mallory’s RAF Fighter Command.

It was on 12 June that British aircraft sighted groups of three U-boats for the first time, and on the next day a Sunderland of No. 228 Squadron attacked the pack comprising U-564, U-185, U-415, U-634 and U-159, and damaged the first of these before itself being shot down by anti-aircraft fire.

On 14 June an Armstrong Whitworth Whitley of the RAF�s No. 10 OTU sank Oberleutnant Hans Fiedler’s U-564, which was accompanied by U-185, but was damaged by anti-aircraft fire and then shot down by a Ju 88. The German destroyers Z 24 and Z 32 set out to meet the U-boats and take off U-564�s 18 survivors from U-185.

From 14 June Air Vice Marshal G. R. Bromet’s No. 19 Group of Air Marshal Sir John Slessor’s RAF Coastal Command began to counter the new German tactics with the integrated 'Musketry' air and 'Seaslug' surface operations. Three times per day, seven aircraft were deployed in parallel lines in the search area to the north-west of Finisterre to offer rapid support in the event that any U-boats were sighted. The aircraft involved in 'Musketry' were the Liberator long-range patrol aircraft of the RAF’s Nos 53, 86 and 224 Squadrons, and the USAAF’s 1^st, 4^th and 19^th Anti-Submarine Squadrons, Catalina flying boats of the RAF’s No. 210 Squadron and US Navy’s VP-63 squadron equipped with magnetic anomaly detection (MAD) equipment, Sunderland flying boats of the RAF’s Nos 226 and 228 Squadrons and the RAAF’s Nos 10 and 461 Squadrons, Vickers Wellingtons of the RAF’s No.172 Squadron, No. 304 (Polish) Squadron and No. 311 (Czech) Squadron, and the RCAF’s No. 426 Squadron, Boeing Fortress long-range patrol aircraft of the RAF’s No. 59 Squadron and Halifax long-range patrol aircraft of the RAF’s Nos 58 and 502 Squadrons.

On 14 June the outbound U-68 and U-155 were damaged by the 20-mm cannon fire of four Mosquito heavy fighters of No. 307 (Polish) Squadron, and were forced to turn back to base. In the course of 'Musketry' patrol on 17 June, a Fortress of No. 206 Squadron damaged the outbound U-338. On 19 June the outbound Italian submarine Barbarigo was sunk, probably by an aeroplane of the USAAF. On 21 June the outbound tanker U-462 was slightly damaged by the cannon fire of four Mosquito heavy fighters of Nos 151 and 456 Squadrons, and on 2 July the boat was again damaged, this time by a Liberator of No. 224 Squadron, and also compelled to turn back to base.

On 23 June the returning U-650 was damaged by a Liberator of No. 86 Squadron which was flying escort for the WS.31 and KMF.17 convoys. On 27 June the outbound U-518 was damaged by a Sunderland of No. 201 Squadron. On 3 July two returning boats, Oberleutnant Siegfried Kietz’s U-126 and U-154, were attacked by a Wellington of No. 172 Squadron, and the former sank. On the same day the outbound U-386 was damaged by a Liberator of No. 53 Squadron and Kapitänleutnant Heinrich Hasenschar’s U-628 was sunk by a Liberator of No. 224 Squadron, which was itself damaged by anti-aircraft fire.

On 5 July the returning U-535, U-536 and U-170 could not be found by the ships of the 2^nd Escort Group, which were undertaking a search on the basis of 'Ultra' information, but a Liberator of No. 53 Squadron attacked and sank Kapitänleutnant Helmut Ellmenreich’s U-535 as well as damaging the two other boats although the aeroplane itself was also damaged. On 7 July the outbound U-267 was damaged by a Catalina of No. 210 Squadron. On 8 July Kapitänleutnant Hans-Jürgen Auffermann’s outbound U-514 of the 'Monsun' wolfpack was sunk by a Liberator of No. 224 Squadron using a Mk 24 homing torpedo. On 12 July U-441, with specially strengthened anti-aircraft armament, was damaged by the 20-mm cannon fire of three Beaufighter heavy fighters of No. 248 Squadron and had to turn back with 10 dead and 13 wounded. On 13 July the outbound U-607, U-445 and U-613 were attacked by a Halifax of No. 58 Squadron and a Sunderland of No. 228 Squadron, and the flying boat also also sank Oberleutnant Wolf Jeschonnek’s U-607. On 20 July Kapitänleutnant Günther Krech’s returning U-558 was sunk by a Liberator of the 19^th Anti-Submarine Squadron and a Halifax of No. 58 Squadron.

On 24 July Korvettenkapitän Georg von Wilamowitz-Moellendorff’s outbound tanker U-459 shot down a Wellington of No. 172 Squadron, but was itself damaged and later sunk by a Wellington of No. 547 Squadron. On 28 July Oberleutnant Adolf Schönberg’s outbound U-404 was sunk by a Liberator of No. 224 Squadron and a Liberator of the 4^th Anti-Submarine Squadron, the latter being damaged in the engagement.

On 29 July Kapitänleutnant Wolfgang Sträter’s outbound U-614 was sunk by a Wellington of No 172 Squadron. In defensive actions, U-600, U-462, U-628, U-43, U-558, U-459, U-454 and U-383 each shot down one aeroplane, and German fighters shot down six more.

The standard practice was for the vital U-tankers and damaged boats to be escorted by two to four destroyers (Z 24, Z 23 and Z 32) or torpedo boats (T 5, T 19, T 22, T 24, T 25, Falke, Greif, Möwe, Jaguar and Kondor).

On the British side, support groups were deployed from 20 June west of the Bay of Biscay with cruiser cover against German surface ships. In the first operation, from 20 to 28 June, an aeroplane led the 2^nd Support Group to U-650, U-119 and U-449, and the sloop Starling then rammed and sank Kapitänleutnant Horst-Tessen von Kameke’s tanker U-119, and the combination of Wild Goose, Woodpecker, Kite and Wren sank Oberleutnant Hermann Otto’s U-449. Cover was provided by the light anti-aircraft cruiser Scylla. Relief was provided at five/eight-day intervals by the 40^th Escort Group, the Escort Group B5 (led by the destroyer Havelock), the 2^nd Support Group (led by the sloop Wild Goose), the 5^th Support Group (led by the frigate Nene), the Escort Group B1 (led by the destroyer Hurricane), a destroyer group consisting of the Canadian Iroquois and Athabaskan, and Free Polish Orkan, and the Escort Group B5 (including the escort carrier Archer), covered by the light cruisers Bermuda and Glasgow).

On 30 July an outbound pack consisting of the tankers U-461 and U-462 and the combat boat U-504 was spotted by a Liberator of No. 53 Squadron and reported to nearby aircraft as well as Commander F. J. Walker’s 2^nd Support Group. In repeated attacks involving seven aircraft, Korvettenkapitän Wolf-Harro Stiebler’s U-461 was sunk by a Sunderland of No. 461 Squadron, Leutnant Bruno Vowe’s U-462 by a Halifax of No. 502 Squadron and Korvettenkapitän Wilhelm Luis’s U-504 by the sloops Kite, Woodpecker, Wren and Wild Goose.

On 1 August Kapitänleutnant Burckhard Hackländer’s outbound U-454 was sunk by a Sunderland (itself shot down) of No. 10 Squadron and Kapitänleutnant Horst Kremser’s outbound U-383 sank following damage inflicted by a Sunderland of No. 228 Squadron. On 2 August Korvettenkapitän Alexander von Zitzewitz’s outbound U-706 was sunk by a Liberator of the 4^th Anti-Submarine Squadron and a Handley Page Hampden of No. 415 Squadron, and Oberleutnant Wolf-Dietrich Damerow’s outbound U-106 was sunk by two Sunderland flying boats of No. 228 Squadron and No. 461 Squadron in the vicinity of the 40^th Escort Group, whose ships rescued the survivors. On the same day the outbound U-218 was damaged by a Wellington of No. 547 Squadron, and the torpedo boats T 22, T 24 and T 25, answering U-383's distress signal, rescued U-106's survivors.

These losses forced Grossadmiral Karl Dönitz, commander-in-chief of the German navy since 30 January 1943 but still in day-to-day command of the U-boat arm, to abandon the tactics of group sailings, and postpone further U-boat departures until they had been equipped with the new 'Hagenuk' receiver to warn when ASV.Mk IV radar was being used. The losses among the small number of 'milch cow' U-boats also meant that operations with medium-range boats in distant areas had to be abandoned.