Japanese Castles in Korea 1592–98

Introduction: the very short history of the wajo

The invasions of Korea in 1592 and 1597, the attempt at occupation between those two dates and the desperate rearguard action late in 1598 together make up a military operation unique in Japanese history. Apart from numerous pirate raids on China and Korea, some of which were very large in scope, and the annexation of Ryukyu (modern Okinawa prefecture) by the Shimazu clan in 1609, the Korean expedition remains the only occasion within a period of 1,000 years during which the destructive energies of the samurai (Japan's warrior class) were expended on a foreign country.

Japan's Korean expedition - known to Koreans as the Imjin War - was also the last military campaign to be set in motion by Toyotomi Hideyoshi (1536-98), and was to prove a disastrous end to the glorious military career of a brilliant general who is regarded as Japan's equivalent of Napoleon Bonaparte. Having risen from the lowest ranks through a mixture of skill and opportunistic cunning, Hideyoshi was adored by his subordinates, who served him with a keen loyalty to a 'soldiers' general' that transcended the legendary fidelity expected of a samurai. In this Hideyoshi had set them a fine example when he served as the most loyal and talented member of the inner circle of generals under Japan's first unifier, Oda Nobunaga (1534-82). Nobunaga, an early enthusiast for the firearms introduced from Europe in 1543, had transformed Japanese warfare, and had taken the first steps towards reuniting the country from the patchwork of competing petty daimyo (feudal warlords) whose squabbles had given the age the name of the Sengoku Jidai, the Age of Warring States.

When Nobunaga was murdered in 1582, Toyotomi Hideyoshi became his avenger, and by a series of rapid offensives overcame his fellow generals to inherit Nobunaga's former domains. Three massive campaigns followed: the invasion of the island of Shikoku in 1585; the conquest of the island of Kyushu in 1587; and the defeat of the powerful Hojo family near modern Tokyo in 1590. Within a year all the other daimyo had submitted to him, so that by 1591 Japan was reunited under the son of a peasant.

If Hideyoshi had been content to stop there his place in Japanese history would have been assured. But his campaigns of the 1580s had involved the successful deployment of armies numbered in many tens of thousands and their safe transport by sea. By 1591 everything looked possible to him, even the conquest of China, a dream that he had entertained for several years. Geography, if nothing else, suggested that to carry out such an outrageous scheme - which would have to be aimed at Beijing, the capital of the Ming dynasty - a Japanese invasion would have to proceed via the Korean Peninsula. When the Korean king refused to allow the Japanese unimpeded progress through his country the planned Chinese war became a Korean war.