[1] 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 under the command of Kapitänleutnant Heinrich Schuch as part of the 6th U-boat Flotilla.

[1] Between August 1939 and March 1941, U-37 conducted eleven combat patrols, sinking 53 merchant ships, for a total of 200,063 gross register tons (GRT); and two warships, the British Hastings-class sloop HMS Penzance, and the French submarine Sfax (Q182).

The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 metric horsepower (740 kW; 990 shp) for use while submerged.

[6] U-37 left Wilhelmshaven on 5 October 1939 to conduct operations in the North Atlantic now under the command of Korvettenkapitän Werner Hartmann.

As on his previous patrol, Hartmann sank eight ships, this time three British, two Norwegian, one Danish, one French and one Greek.

Again, Hartmann proved successful, sinking three ships; the Norwegian Tosca, the Swedish Sveaborg and the British Stancliffe.

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.

[13] On 24 September, U-37 departed Lorient on Victor Oehrn's fourth patrol, in which he would sail to the North Atlantic.

The fourth ship sunk was the British Stangrant, sailing as part of convoy HX 77 from Halifax to the United Kingdom.

[14] After over a month in port, U-37 departed with a new captain, Oberleutnant zur See Asmus Nicolai Clausen on 28 November for operations around north-west Africa and Spain.

The Swedish Gwalia and Daphne and the British Jeanne M were sailing as part of convoy OG 46 from Britain to Gibraltar.

The French vessels, the oiler Rhône and the submarine Sfax belonged to Vichy France and were sunk in error.

The U-boat then returned to Lorient on 18 February after spending 20 days at sea and sinking 4,781 GRT of shipping.