Hideyoshi launched the invasion of Korea in 1592, with the aim of conquering Korea first and using it as a base for eventual conquest of China. As things turned out, although the superior Japanese army made great progress at first (starting from Busan, taking Pyongyang and most of the peninsula in 3 months), they could not advance any further and were pushed out of Korea eventually, in 1598. The way I see it, the Japanese had severe strategic shortcomings that made the stated goals (conquest of Korea and China) wildly unrealistic:
- The Japanese navy could not match the Koreans, and thus were mostly limited to guarding the Tsushima supply route, greatly hampering the land advance
- They met with strong guerrilla resistance, tying up scarce manpower in defensive operations
- Korea was an important tributary state to China at the time, and the latter would not sit idly by
These shortcomings would have been obvious to any competent commander, and Hideyoshi was no slouch. So what reasons did Hideyoshi have to initiate the invasion in the first place? Were there political intrigues, domestic issues, was this a golden opportunity (relatively speaking), or just plain arrogance/stupidity on Hideyoshi's part?