Weddigen entered the Navy in 1901 and was from 1906 to 1907 stationed in Tsingtau. On September 15, 1910 he became commander of an U-boat and in October 1911 he took over the command of U9. His famous military exploit as U9's commander was the sending to the bottom of sea the British cruisers Aboukir, Cressy and Hogue (each 12.000 G.R.T.) on September 22, 1914 in the south of the North Sea, for which he was awarded the Pour le Mérite. On October 15, 1914, Weddigen's U9 destroyed the British cruiser Hawke (7.350 G.R.T.) and in February 1915 he destroyed 4 merchant ships (totalling 12.934 G.R.T.), while in command of U29. Returning from the attack on the British battle-fleet near the Orkneys, U29 was rammed by the Dreadnought and sank with the whole crew (March 18, 1915). Weddigen was one of the best known German naval heroes.
Eggstein, Rudolf, 'Seeheld Otto Weddigen dem deutschen Volke und seinem Heere dargestellt, Leipzig: Schloessmann, 1915.
Pemsel, Helmut, Biographisches Lexikon zur Seekriegsgeschichte. Seehelden von der Antike bis zur Gegenwart, Koblenz: Bernard & Graefe, 1985.
Unser Seeheld Weddigen. Sein Leben und seine Taten dem deutschen Volke erzählt, Berlin: Scherl, 1915.