In 1592 and 1597, Japanese warlord Toyotomi Hideyoshi led the invasion of Korea by daimyo and their troops. This war is generally referred to as the Imjin War or Seven-Year War. Factional infighting in the Joseon court, the inability to assess Japanese military capability and failed attempts at diplomacy led to poor preparation on the Joseon's part. The element of surprise and use of European firearms by the Japanese left most of the southern peninsula occupied within months, with both Pyongyang and Seoul captured.
Local resistance, however, slowed down the Japanese advance and decisive naval victories by Admiral Yi Sun-shin left control over sea routes in Korean hands, severely hampering Japanese supply lines. Chinese forces from the Ming refused to give aid when asked for help. Eventually, Joseon repelled these invasions alone. During the war, Koreans developed powerful firearms and high-quality gunpowder and the Turtle ships, the first cannon-bearing ironclad warships in world history. Even though Korea won the Seven-Year War, it left deep scars in Korea. Farmlands were devastated, irrigation dikes were destroyed, villages and towns were burned down, the population was first plundered and then dispersed, and tens of thousands of skilled workers (celadon ware makers, craftsmen, artisans, etc) were either killed during the war or kidnapped to Japan as captives to help Japanese develop their crafts. In 1598 alone, the Japanese took some 38,000 ears as horrific trophies. The long war reduced the productive capacity of farmlands from 1,708,000 kyol to 541,000 kyol. Pillage and foraging by Chinese troops only added to the unmitigated tragedy of a war from which the peninsula kingdom never fully recovered. Following the war, relations between Korea and Japan had been completely suspended. Japan was cut off from the technology of continental Asia. After the death of Toyotomi Hideyoshi, however, negotiations between the Korean court and the Tokugawa shogunate were carried out via the Japanese lord on Tsushima. In 1604, Tokugawa Ieyasu, needing to restore commercial relations with Korea in order to have access to the technology of the mainland again, met Korea's demands and released some 3000 captive Koreans. As a result, in 1607, a Korean mission visited Edo, and diplomatic and trade relations were restored on a limited basis.
- Jeongmallok , journal of events during this period.