German submarine U-37 was a Type IXA U-boat of the German Navy (Kriegsmarine) during World War II. The submarine was laid down on 15 March 1937 at the DeSchiMAG AG Weser yard in Bremen, launched on 14 May 1938, and commissioned on 4 August 1938 as part of the 6th U-boat Flotilla.

Between August 1939 and March 1941, U-37 conducted eleven combat patrols, sinking 53 merchant ships, for a total of ; and two warships, the British , and the . U-37 was then withdrawn from front-line service and assigned to training units until the end of the war. On 5 May 1945 the U-boat was scuttled. U-37 was the sixth most successful U-boat in World War II in terms of tonnage sunk.

Design and construction As one of the eight original Type IX submarines, later designated IXA, U-37 had a displacement of when at the surface and while submerged. The U-boat had a total length of , a pressure hull length of , a beam of , a height of , and a draught of . The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to .

The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-37 was fitted with six torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one SK C/32 naval gun, 180 rounds, and a as well as a C/30 anti-aircraft gun. The boat had a complement of forty-eight.

U-37 was one of four Type IX submarines ordered on 29 July 1936. The submarine was laid down at AG Weser's Bremen shipyard on 15 March 1937, as yard number 942. She was launched on 14 May 1938 and commissioned on 4 August 1938.

Service history

First patrol In preparation for the German invasion of Poland and potential war with the United Kingdom and France, Admiral Karl Dönitz, commander of Germany's submarine forces, ordered a deployment of U-boats to the Atlantic in August 1939. U-37 left Wilhelmshaven, with Heinrich Schuch in command, on 19 August 1939, passing north of the British Isles while en-route to the submarine's patrol area off Spain and Portugal rather than via the English Channel. The boat operated for nearly four weeks in the North Atlantic, returning to port on 15 September 1939.

Second patrol U-37 left Wilhelmshaven on 5 October 1939 to conduct operations in the North Atlantic now under the command of Werner Hartmann. It was intended that Hartmann would direct a group of German submarines (known as a wolfpack) against allied convoys. Hartmann's wolfpack consisted of six submarines, three Type IX submarines and three smaller Type VIIs, from two different flotillas which had never exercised together. On the way to the patrol area, U-37 sank two merchant ships, the Swedish Vistula on 8 October and the Greek Aris on 12 October. The wolfpack was then ordered to attack the Anglo-French convoy KJF3, inbound from Jamaica, but U-37 was too far away to direct the operation as intended, and was unable to catch the convoy, although U-37 did manage to sink a straggler from the convoy, the French cargo ship Vermont. The group was then ordered to attack Convoy HG 3, sailing from Gibraltar to Liverpool, England. U-37 sank the British cargo steamship Yorkshire from the convoy, with two more ships being sunk by and . U-37 continued her patrol further south, sinking three ships to the west of the Straits of Gibraltar on 24 October, the British Menin Ridge, Ledbury and Tafna, before being attacked by the British destroyers and with depth charges before the submarine managed to escape. On the return journey, U-37 sank the Greek Thrasyvoulos on 26 October. Hartmann returned his boat to port on 8 November after nearly five weeks at sea. U-37 had sunk eight ships during the patrol: four British, two Greek, one French and one Swedish. The attempt to control wolfpacks from submarines at sea had proved a failure, with Hartmann reporting that he had found it impossible to coordinate the operations of other submarines, and future wolfpack operations would be controlled from the shore.

Third patrol On 1 January 1940 U-37 was reassigned to the 2nd U-boat Flotilla based at Wilhelmshaven. On 28 January 1940 the U-boat departed for the North Atlantic, with Werner Hartmann still in command. On 4 February 1940, U-37 sank two ships east of Sumburgh Head, Shetland, the Norwegian steamship Hop and the British Leo Dawson. On 8 February the submarine landed two agents at Donegal Bay, Ireland, These agents were soon arrested, however. On the way to the assigned patrol area U-37 sank the Norwegian merchant ship Silja on 10 February and the British trawler Togimo on 11 February, before being diverted to the Western end of the English Channel in an unsuccessful attempt to intercept the aircraft carrier . After being released from this attempt, U-37 sank the Danish steamship Aase on 15 February. After reaching the patrol area, U-37 was directed against a convoy detected by German signal intelligence, sinking three ships in two days, the Pyrrhus on 17 February and the Greek Ellin and the French P.L.M. 15 on 18 February, although Pyrrhus and P.L.M. 15 were stragglers from separate convoys, and Ellin was sailing independently. U-37 returned to Wilhelmshaven on 27 February. As on his previous patrol, Hartmann sank eight ships, this time three British, two Norwegian, one Danish, one French and one Greek. Hartmann claimed 43,000 tons of shipping sunk in this patrol, although the actual figure was 24,539 tons.

Fourth patrol

U-37 departed Wilhelmshaven on 30 March for Hartmann's third consecutive patrol, with the submarine's initial duty being escorting the auxiliary cruiser as the raider broke out into the Atlantic. After leaving Atlantis, U-37 reverted to a normal patrol, sinking two ships, the Swedish tanker Sveaborg and the Norwegian Tosca north of the Faroe Islands on 10 April and the British steamship Stancliffe north-east of Unst, Shetland, on 12 April. On 13 April, U-37 attempted to attack a British cruiser, but torpedo defects caused the attack to fail. After patrolling for over two weeks, the U-boat returned to Wilhelmshaven on 18 April.

Fifth patrol Hartmann was replaced as commander of U-37 on 6 May 1940 by Victor Oehrn, with Hartmann becoming a staff officer for Admiral Karl Dönitz. U-37 departed from Wilhelmshaven on 15 May for a patrol around Portugal and Spain. On 19 May, U-37 sank the Swedish merchant ship Erik Frisell with gunfire, and on the night of 22/23 May attacked the British Dunster Grange. Several torpedoes were fired at the merchant ship, but torpedo failures meant that none of the torpedoes struck home. U-37 then attacked with her gun, hitting Dunster Grange, but return fire from the British ship caused U-37 to break off the attack. Oehrn reported the torpedo failures by radio, and in response, Dönitz ordered all U-boats to switch from magnetic to impact detonators. The contact detonators were more successful, and U-37 torpedoed and sank the Greek steamship Kyma the next day. On 27 May U-37 torpedoed and sank the steamship Sheaf Mead. Observing that Sheaf Mead was painted gray and was fitted with deck guns, Oehrn concluded that the ship was an auxiliary cruiser or a Q-ship, and made no attempt to assist the survivors of the sinking. This refusal to assist the survivors was later cited by prosecutors at the Nuremberg trials as an example of German brutality. Later that day, U-37 stopped the Argentinean cargo ship Uruguay, sailing from Rosario to Limerick with a cargo of maize. After examining Uruguays papers, U-37 sank her with scuttling charges. Uruguays crew of 28 were left in their lifeboats. 15 died, 13 survived. U-37 sank the French cargo liner and trawler Julien on 28 May, and on 29 May sank the French steamship Marie José and the British tanker Telena. On 1 June U-37 sank the Greek steamship Ioanna and on 3 May the Finnish Snabb. U-37 returned to Wilhelmshaven on 9 June, having used up all her torpedoes. This was the submarine's most successful mission, hitting eleven ships, sinking ten of them. Three French ships were sunk, two Greek, two British, one Swedish, one Argentinian, one Finnish; one British ship was damaged.

Sixth patrol U-37 sailed from Wilhelmshaven on 1 August 1940, again with Victor Oehrn in command. This week and a half long patrol in the Atlantic off the west coast of Ireland resulted in the sinking of a single British ship, Upwey Grange. U-37 returned to port on 12 August, but rather than head back to Wilhelmshaven, she made for Lorient in France, where the 2nd U-boat Flotilla was now based.

Seventh patrol For the first time, U-37 began a patrol from a location other than Germany, at Lorient on 17 August, with Oehrn in command once more. The submarine was to focus on operations in the mid-Atlantic. On 23 August, U-37 sank the Norwegian steamship Keret and the British Severn Leigh, and early on 24 sank the British steamship Brookwood. Later that day, U-37 attacked Convoy SC 1, sinking the British sloop and then Blairmore from the same convoy early on 25 August. Attacks by air and surface escorts forced the patrol to be abandoned early, but this did not stop U-37 from sinking the steamship Yewcrest later on 25 August and the Greek Theodoros T on 27 August. U-37 returned to Lorient on 30 August 1940, having sunk seven ships during this voyage, including Penzance (which Oehrn identified as a destroyer).

Eighth patrol On 24 September 1940, U-37 departed Lorient on Oehrn's fourth patrol, in which the submarine would patrol west of the British Isles. On 27 September, U-37 sank the Egyptian Georges Mabro and on 28 September, the submarine encountered SS Corrientes, which had been torpedoed by on 26 September while part of a westbound convoy, and whose crew had abandoned her, but remained afloat. U-37 sunk the abandoned wreck with a torpedo and shellfire. U-37 was then directed to operate as a weather reporting boat further to the west, where the submarine sank the steamships Samala and Heminge on 30 September. On 6 October, U-37 sank the tanker British General, and on 13 October, when on the return journey to France, sank Stangrant, a straggler from Convoy HX 77 from Halifax to the United Kingdom. The U-boat returned to Lorient on 22 October 1940, having sunk six ships, for a tonnage of 23,200 GRT. These continuing successes resulted in Oehrn being awarded the Knight's Cross of the Iron Cross, before leaving the submarine to take over Hartmann's role as first staff officer for Admiral Dönitz. U-37 had by this time sank ships for a tonnage of 180,000, which was the most ships sunk by a U-boat at this time and the second highest tonnage total, behind U-48. U-37s chief engineer, Gerd Suhren, was also awarded the Knight's Cross for keeping the submarine operational in the face of multiple faults.

Ninth patrol