U-873 is remembered for the controversial treatment of its crew as prisoners of war and the death of commanding officer Kapitänleutnant Friedrich Steinhoff in a Boston jail cell.

Six months after Steinhoff's death, his brother was one of the Operation Paperclip rocket scientists from Peenemünde arriving in the United States to work at White Sands Missile Range.

The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines plus two MWM RS34.5S six-cylinder four-stroke diesel engines for cruising, producing a total of 9,000 metric horsepower (6,620 kW; 8,880 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.

[4] U-873 was commissioned on 1 March 1944 under the command of Kapitänleutnant Friedrich Steinhoff and assigned to the 4th U-boat Flotilla for training in the Baltic Sea from the base in Stettin.

[1] The crew of the new submarine was assembled around a nucleus of Engineering Officer Helmut Jürgens, Quartermaster Albert Finister, and ten other survivors from U-604, which had been sunk off the coast of Brazil on 11 August 1943.

Subsequent investigation concluded personal possessions of the U-boat crewmen were looted contrary to provisions of the Geneva Convention.

He then commanded U-511 during rocket launching experiments of 1942 in cooperation with his brother Ernst Steinhoff, who was Director for Flight Mechanics, Ballistics, Guidance Control, and Instrumentation at the Peenemünde Army Research Center.

[11] U-873 crewman Georg Seitz reported Steinhoff's face was bleeding and swollen when he returned to his cell after being questioned by a civilian ONI interrogator who ordered a husky United States Marine Corps guard to slap the officer.

[5] On 19 May 1945 Steinhoff bled to death in his Boston jail cell from wrist wounds, possibly inflicted with the broken lens of his sunglasses.