The Battle of Kōan, also known as the Second Battle of Hakata Bay, is the second attempt by the Yuan Dynasty founded by the Mongols to invade Japan; they had failed seven years earlier, in the Battle of Bun'ei.

In the summer of 1281 they gather two invasion forces and invade.

the Japanese defenders are aided by major storm that sinks a sizable portion of the Mongolian fleets.

Ultimately, these invasion attempts are decisively repulsed shortly after their initial landings; the Japanese call the storm that had chased away their invaders kamikaze ("divine wind"), a prestigious name later used in the Second World War for aerial suicide attacks.