1.   As World War II raged, agents took up posts along the East Coast and watched for German submarines and saboteurs.

2.   At MIT, Dr. Isidor Rabi was preparing the theoretical underpinning for more potent radar systems that would detect and track targets like German submarines.

3.   Attacks by a German submarine on the passenger liner Lusitania drew an isolationist America into the trenches of World War I.

4.   A U-boat was a German submarine, from the German word Unterseeboot.

5.   Alf Cheetham, one of the officers on the Endurance, drowned when a German submarine torpedoed his minesweeper just before the armistice.

6.   Falsely accused by neighbors of signaling to German submarines from the windows of their cottage, the couple was ordered by the police to leave Cornwall and move inland.

7.   German submarines were everywhere.

8.   German submarines, infamous for the terror they caused in two world wars, now are sinking competitors in the world arms market.

9.   German submarines, infamous for their performance in two world wars, are now sinking competitors in the world arms market.

10.   German submarines today are the subcompacts of the submarine world, one reason for their popularity with smaller countries.