The Battle of the Bay of Biscay, or Operation Bernau, was a naval action that took place on 28 December 1943 during World War II as part of the Atlantic campaign. The battle took place in the Bay of Biscay between two light cruisers of the British Royal Navy, and a destroyer and a torpedo boat flotilla of the German Kriegsmarine hoping to intercept and escort a blockade runner. The battle was fought as part of the Allied Operation Stonewall, which was to intercept German blockade runners off the west coast of France. In the confused action that followed the two British cruisers and respectively sank T26, together with her sister ship T25 and the destroyer Z27.
Background
In late December 1943 a German Kriegsmarine destroyer flotilla, reinforced by six large Elbing-class torpedo boats, was ordered to the Bay of Biscay in order to escort into a French port the blockade runners Osorno and Alsterufer, which were carrying vital cargo from Japan. The Germans codenamed this Operation Bernau. The blockade runner Osorno reached the Gironde on 26 December, but struck a wreck in the estuary after being attacked by the RAF. She was beached and subsequently unloaded offshore. Meanwhile, Alsterufer, carrying tungsten (Wolfram) and rubber, was still much further behind.
Korvettenkapitän Franz Kohlauf sailed from Brest on the morning of 27 December with the torpedo boats T23, T24, and T22. The 8th Destroyer Flotilla under Kapitän zur See Hans Erdmenger put out from the Gironde with destroyers , Z37, and , accompanied by two torpedo boats, , under the command of Korvettenkapitän Wirich von Gartzen, and T27.
The British Admiralty were also aware of the impending arrival of Alsterufer through the decryption of German Enigma messages at Bletchley Park and sent out dispatches to the nearest ships in the area for the interception. The closest ship, the light cruiser , which had sailed from the Azores on 24 December, was soon joined by . In support, but further away; had been ordered out from Gibraltar; steamed past Lisbon; and HMNZS Gambia was in the Western Atlantic.
By 04:00 the next day the 4th Flotilla was 300 miles due south of Cape Clear, the 8th Flotilla standing to the south, and were ready to meet Alsterufer. She was however nowhere to be seen. The German flotillas were completely unaware that during the previous afternoon a B-24 Liberator bomber of No. 311 (Czechoslovak) Squadron RAF had attacked and set Alsterufer on fire. Abandoned by her crew, the ship was finished off by Liberators of No. 86 Squadron. This released the Glasgow and Enterprise, who were some 300 nautical miles south-west of the German forces and were now steaming eastwards along the 45th Parallel.
Just after midday, Erdmenger's 8th Destroyer Flotilla sighted Kohlauf's 4th Flotilla to the east, whereupon the torpedo boats turned east astern of the northernmost destroyers, taking station on their port side.
Battle
Allied aircraft had already reported the position of the German ships about 1300. About the same time a lone German Focke-Wulf Fw 200 Condor sighted and attacked both cruisers only to be repelled by anti-aircraft gunfire. The German aircrew immediately turned north-east, reporting the position of the British cruisers more than half an hour later to Erdmenger. Captain Charles Clark on HMS Glasgow, assuming that he had been reported then also turned north-east, working around Erdmenger's position to intercept. The sea was becoming rougher and the wind had increased to 30 knots, making sailing difficult for the destroyers and torpedo boats.
Sailing into rough seas and gale force winds, Glasgow sighted the destroyers at 1332 hours at a range of 16 miles. The two cruisers then intercepted at full speed and altered course to cut the German ships off from their base. Soon after Clarke gave the order for Glasgow to open fire with her 6-inch 'A' and 'B' turrets using her Type 273 radar for ranging. Enterprise opened fire a few minutes later. The two leading German destroyers however remained unscathed as shells splashed 100–150 metres from their targets. The Germans counter-attacked: Z23 launched six torpedoes, three from each bank of tubes, when the range was down to 17,000 metres, but missed. Both destroyers also opened up with their 15 cm guns and their first shots fell only 200 metres over on Glasgow's port quarter. At about 1405 hours, a German shell hit Glasgow which exploded in 'A' boiler room, killing two members of the port pom-pom crew and wounding six others. Enterprise was continually straddled by near misses.