German submarine U-739

German submarine U-739 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 17 April 1942 by Schichau-Werke, Danzig as yard number 1536, launched on 23 December 1942 and commissioned on 6 March 1943 under Leutnant zur See Ernst Mangold.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-739 had a displacement of 769 t when at the surface and 871 t while submerged. She had a total length of 67.10 m, a pressure hull length of 50.50 m, a beam of 6.20 m, a height of 9.60 m, and a draught of 4.74 m. The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2800 to 3200 PS for use while surfaced, two AEG GU 460/8–27 double-acting electric motors producing a total of 750 PS for use while submerged. She had two shafts and two 1.23 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 17.7 kn and a maximum submerged speed of 7.6 kn. When submerged, the boat could operate for 80 nmi at 4 kn; when surfaced, she could travel 8500 nmi at 10 kn. U-739 was fitted with five 53.3 cm torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm SK C/35 naval gun, 220 rounds, and two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.

Service history
The boat's career began with training at 8th U-boat Flotilla on 6 March 1943, followed by active service on 1 November 1943 as part of the 9th Flotilla. Just two months later she transferred to 13th Flotilla for the remainder of her service.

In eight patrols she sank one warship for a total of 625 tons.

Wolfpacks
U-739 took part in eight wolfpacks, namely:
 * Isegrim (16 – 27 January 1944)
 * Werwolf (27 January – 2 February 1944)
 * Boreas (28 February – 5 March 1944)
 * Keil (16 – 20 April 1944)
 * Donner & Keil (20 April – 3 May 1944)
 * Trutz (7 – 10 July 1944)
 * Greif (5 August – 26 September 1944)
 * Rasmus (6 – 13 February 1945)

Fate
U-739 surrendered on 13 May 1945 at Emden. Sunk later on 16 December 1945, in position 56.16667°N, -10.08333°W in Operation Deadlight.