The Japanese invasion of Korea (1592-98) has recently been called Asia's first "regional world war." It marked the first time in Asian history that massive armies equipped with modern weaponry faced one another on the field of battle. The Japanese armies commanded by the warlord Toyotomi Hideyoshi were arguably the most skilled in the world at the time, yet in the end the Japanese were defeated by a Sino-Korean alliance in tandem with Korean guerrillas. Looking at the primary documents of the war, it seems apparent that military technology was the single most important, but not the only, factor that shaped the direction and determined the outcome of the war. This article presents an overview of some of the major military technologies utilized by the belligerents and challenges conventional interpretations of the conflict, passed down through the centuries, that claim Japan's defeat was due to superior allied numbers and Hideyoshi's death.