U-156, built by the Atlas Werke in Bremen, was originally one of seven Deutschland class U-boats designed to carry cargo between the United States and Germany in 1916.

The U-156 was scheduled to meet with the U-157 and a small Spanish flagged merchant vessel in an attempt to transit prohibited materials past the British blockade to Germany.

A mine laid by U-156 is often credited with the loss of the cruiser USS San Diego on 19 July 1918, ten miles southeast of Fire Island, New York.

[5][6][7] On 21 July 1918 U-156 opened fire on a beach and marsh within the boundaries of the American town of Orleans, Massachusetts, and several nearby merchant vessels.

She sank 21 fishing boats in the Gulf of Maine area, from Cape Cod to the Bay of Fundy, ranging from the 72 GRT ton schooner Nelson A.

They manned and armed the vessel, and used it in conjunction with the submarine to capture and sink seven other fishing boats in the Grand Banks area, before eventually scuttling her.

[11] On 25 September 1918 and in the following days, U-156 failed to report that she had cleared the Northern barrage minefield between the United Kingdom and Norway on her return voyage to Germany.