German submarine Bremen

Bremen was a blockade-breaking German merchant submarine of World War I. Developed with private funds and operated by the North German Lloyd Line, she was one of the first of seven U-151 class U-boats built and one of only two used as unarmed cargo submarines.

Construction
Bremen was built together with her sister ship Deutschland in 1916 by the Deutsche Ozean-Reederei, a private shipping company created for the enterprise, a subsidiary company of the North German Lloyd shipping company (now Hapag-Lloyd) and the Deutsche Bank. She was constructed without armaments, with a wide beam to provide space for cargo. The cargo capacity was 700 tons (much of it outside the pressure hull), relatively small compared to surface ships.

Bremen was one of seven submarines designed to carry cargo between the United States and Germany in 1916, through the naval blockade of the Entente Powers. Mainly enforced by Great Britain's Royal Navy, the blockade had led to great difficulties for German companies in acquiring raw materials which could not be found in quantity within the German sphere of influence, and thus substantially hindered the German war effort.

Five of the submarine freighters were converted into long-range cruiser U-boats (U-kreuzers) equipped with two 105mm deck guns, and only two were completed according to the original design: the Deutschland and the Bremen.

Maiden voyage and disappearance
The Bremen departed Bremerhaven in September 1916 for Norfolk, Virginia, commanded by Kapitaenleutnant Karl Schwartzkopf, and reportedly carrying financial credits for Simon Lake to begin building cargo submarines for Germany. She did not complete this voyage and her fate is a mystery. Several views have been put forth as to the nature of her fate.

One source records that a submarine believed to have been the Bremen was sighted 300 mi south of Iceland on a course for Baltimore and units of the 10th Cruiser Squadron were dispatched to intercept it; HMS Mantua reported ramming a heavy, submerged object. However, the official log of HMS Mantua makes no mention of this, so it appears to be a myth.

Another source states that Bremen was sunk by British submarine HMS G13. In March 1917, G13 was on patrol off Shetland, covering the exit by U-boats from the North Sea. There she sighted a submarine identified as Bremen, and fired 2 torpedoes, which both missed. Turning, G13 fired again, first with her starboard beam, and continuing her turn with her port beam torpedoes; both these also missed. Then a final shot, with her stern tube, at a range of 7000 yards, was rewarded with an explosion, and Bremen was believed sunk. The Admiralty, however, felt this was inconclusive, and withheld credit for the hit.

Yet another source regards her as lost, probably as a result of hitting a mine. In the absence of any firm evidence, the cause of Bremen's loss remains a mystery.