 These ships, which came to be called "torpedo boat destroyers" (and later simply "destroyers"), initially were purely defensive, both attacking the torpedo boat threats and serving as expendable screens intercepting torpedoes intended for larger ships.In time they became larger and took on more roles, including making their own torpedo attacks on valuable enemy ships as well as defending against submarines and aircraft.Later yet they were armed with guided missiles and eventually became the predominant type of surface warship in modern era.