Submarines deny the sea while surface ships exercise control

South Korea's submarines are central to naval operations, especially sea denial. They can stop an opponent from using a maritime area, while sea control requires a navy to move forces, sustain commerce, and launch operations through it. A submarine cannot provide air defence for a merchant convoy. Surface combatants are therefore still needed to escort shipping and protect movement. The distinction explains why an expanding submarine force does not remove the requirement for multi-purpose destroyers.