Therefore, North Korea inflicted massive damage by the naval mine.

From the 1950s, Korea purchased and used American minehunting vehicles, called Geumhwa, Geumsan, Namyang classes.

The Korean Navy felt an urgent need to modify existing coastal submarines or to introduce new ships.

It also minimized metallic equipment to tightly control the magnetic material inside the ship.

Steel objects that are brought into the ship, like canned food, are heavily restricted and strictly controlled.