Two of these U-boats were lost. The first, U-78 (Oblt. Johann Vollbrecht), sailed on 27 October from Heligoland for a minelaying mission off the Scottish East Coast, but she was torpedoed and sunk the same day by the British submarine G2 in the central North Sea, roughly 280 nautical miles (520 km; 320 mi) east of the Firth of Forth.