Island-class and Castle-class patrol vessels once operated alongside a larger minesweeping force that could support patrol work. The modern comparison describes expanding missions and a patrol fleet reduced to single digits. An adapted fishing-boat design can still provide sensors and presence where an area needs watching. For many maritime security tasks, being available in the right place matters more than carrying a destroyer's weapons. Using a Type 45 or Arleigh Burke for such work consumes a much more expensive ship's time.
Notable Point · 1:08:33-1:10:11
Why maritime security depends on patrol-vessel numbers
Lightly armed patrol ships provide routine presence without tying down major combatants.