"Submarine warfare" refers to military operations that involve the use of submarines to attack and defend against enemy ships or submarines beneath the surface of the water. Full definition
The Enemy Below is a study of submarine warfare from the vantage point of both sides. (rottentomatoes.com)
In April, 1917, when Germany reopened unrestricted submarine warfare and when the last peace proposal had been turned down, America entered the war. (religion-online.org)
As the British placed a strict blockade around the German ports, Germany retaliated by extensive submarine warfare. (religion-online.org)