Korea suffers devastating foreign invasions at the end of the sixteenth century.

The first comes shortly after Toyotomi Hideyoshi ends Japan's internal disorder and unifies the islands.

His eventual goal is to put China under his control, and he launches an invasion that puts some one hundred and sixty thousand Japanese soldiers at Pusan in 1592.

At this, the Joseon court takes flight to the Yalu River, infuriating ordinary Koreans and leading slaves to revolt and burn the registries.

Japanese forces march through the peninsula at will.

In the nick of time, however, Korean admiral Yi Sun-sin builds the world's first armor-clad ships, so-called "turtle ships" encased in thick plating with cannons sticking out at every point on their circular shape, which destroy Japanese fleets wherever they are found.

The Korean ships cut Japan's supply routes, and, combined with the dispatch of Ming forces and so-called "righteous armies" that rise up in guerrilla warfare (even Buddhist monks participate), cause the Japanese to retreat to a narrow redoubt near Pusan.