Naval mine ship, HMHS "Britannic", which was the sister ship of the RMS "Titanic." During World War II, the U-boat fleet, which dominated much of the battle of the Atlantic, was small at the beginning of the war and much of the early action by German forces involved mining convoy routes and ports around Britain. German submarines also operated in the Mediterranean Sea, in the Caribbean Sea, and along the U.S. coast. Initially, contact mines (requiring a ship to physically strike a mine to detonate it) were employed, usually tethered at the end of a cable just below the surface of the
German hospital ship Ophelia HMS "Undaunted", while laying mines off Haak lightship. German command sent out a hospital ship to supposedly search for survivors. Suspicions were aroused when British intelligence learned that "Ophelia" was using a wireless radio set, at that time unusual for a hospital ship, to communicate with the German wireless base at Norddeich station. In addition to using wireless radio she was using coded wireless transmissions; secret codes or their use are forbidden on hospital ships. While in the area, British submarine, HMS "D8", shadowed the German ship. When the "Ophelia" noticed the sub she began to flee the area, further