On April 13, 1592, the Imjin War broke out just as Yi had foreseen. Japan occupied nearly all the land of Josun dynasty which was not prepared for war and tried to supply military provisions through the sea route of Jeolla-do province. Yi had already prepared for war, so he led his navy to victory in every engagement he fought during seven years of war with the Japanese. In the battle of Hansan, using 'crane wing' formation he captured and sank fifty nine of the seventy-three Japanese ships. And in the battle of Myongnyang, he defeated 333 enemy ships with 13 ships his own. This victory has regarded as one of the miracle victories of the world.