Lunar and Gregorian calendar conversion can shift whether the opening actions are labeled May or June. The invasion also addressed a political problem created by unification: a mass of armed retainers could not be demobilized without risk, yet keeping them at home threatened the new regime. An external war promised plunder, preserved military readiness, and kept the army close enough to recall. The explanation does not excuse aggression, but it clarifies the internal logic behind Hideyoshi's decision. Korea was close enough that the army could also serve as an implicit reserve against renewed challenges inside Japan.
Chapter · 8:24-10:19
Why Japanese unification fed the invasion of Korea
Japan's recent civil wars left Toyotomi Hideyoshi with a large experienced army whose continued employment abroad could reinforce his fragile domestic settlement.