After Japan was unified in a series of wars, General Hideyoshi decided to invade China and eventually India. It was decided to conquer Korea first as it was on the way. Initially the Japanese were successful, taking Seoul in three weeks and reaching Pyongyang. But the invasion bogged down. Increased Korean resistance, Chinese intervention, and the famous turtle ships all conspired to defeat the Japanese.
This war, known as the Hideyoshi War or Imjin War, began in 1592 and ended in 1598 with the withdrawal of Japanese troops. Koreans are justly proud of the turtle ship, the first ironclad warship in world history, first used in 1592 and mounting several cannon, some of which could hurl incendiary devices.
When western sailing ships first reached the Pacific, they were able to dominate the trade routes. Closer to shore, Asian rowed galleys, even without armor, were able to defeat western warships. In 1886 near Pyongyang, a turtle ship was used against the American ship General Sherman but was ineffective.
Admiral Yi his campaigns and the art of war. Includes pirate wars of the 13th to 15th centuries.
Turtle Ship and Adm. Lee includes an overview of the war.
Turtle Ship with a history of the ship's development.