German submarine U-709

German submarine U-709 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.

Ordered 15 August 1940, she was laid down on 5 May 1941 and launched 14 April 1942. From 12 August 1942 until 2 December 1943, she was commanded by Oberleutnant zur See Karl-Otto Weber, then captained by Oberleutnant zur See Rudolf Ites from 3 December 1943 until 19 February 1944.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-709 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 Garbe, Lahmeyer & Co. RP 137/c 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-709 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
U-709 had five patrols, from 12 August 1942 until 19 February 1944, during which she sank no ships.

Wolfpacks
U-709 took part in 15 wolfpacks, namely:
 * Westmark (6 – 11 March 1943)
 * Amsel (22 April – 3 May 1943)
 * Amsel 3 (3 – 6 May 1943)
 * Rhein (7 – 10 May 1943)
 * Elbe 1 (10 – 14 May 1943)
 * Without name (11 – 29 July 1943)
 * Siegfried (22 – 27 October 1943)
 * Siegfried 3 (27 – 30 October 1943)
 * Jahn (30 October – 2 November 1943)
 * Tirpitz 4 (2 – 8 November 1943)
 * Eisenhart 6 (9 – 13 November 1943)
 * Schill 2 (17 – 22 November 1943)
 * Igel 2 (3 – 17 February 1944)
 * Hai 1 (17 – 22 February 1944)
 * Preussen (22 February – 1 March 1944)

Fate
She has been missing since 19 February 1944 in the North Atlantic. No explanation for its loss. All hands lost.

Previously recorded fate
She was sunk by depth charges from the US destroyer escorts USS Thomas (DE-102), USS Bostwick (DE-103), and USS Bronstein (DE-189) while on patrol north of the Azores; all 52 crew members aboard died. Niestlé disagreed with the official account, and conclude that there was no known explanation for its loss.