Japanese ambassadors asked Korea to permit an army to land and cross the peninsula on its way to attack Ming China. The request was effectively hostile because it targeted Korea's closest ally and would place Japanese forces inside Korean territory. Marching through the peninsula also posed severe terrain and supply problems compared with attacking China more directly by sea. The exchange reveals that the invasion plan depended on Korean territory and maritime transport even though Japan had not prepared to win command of Korean coastal waters.
Notable Point · 48:23-49:41
Japan's demand for passage exposes the invasion's logistics
The demand to land in Korea and march against Ming China was both a threat to Korea and a revealingly difficult plan for sustaining a continental invasion.