Sengoku Period

The Sengoku Period (戦国時代, "Age of Warring States") describes the prolonged political fragmentation of Japan that followed the breakdown of the Ashikaga shogunate's effective authority. Most historians date its beginning to the Ōnin War (1467–1477), a succession dispute that devastated Kyoto and exposed the shogunate's inability to control regional power-holders. Its endpoint is conventionally placed at the Siege of Osaka (1614–1615), when Tokugawa Ieyasu eliminated the Toyotomi house and consolidated the Tokugawa shogunate.

During this era, traditional provincial governors (shugo) were often displaced by upstart warlords through a process called gekokujō ("the lower overcoming the higher"). Independent daimyō built castle towns, codified house laws (bunkokuhō), surveyed land, and maintained standing armies. Warfare was transformed by the introduction of matchlock firearms by Portuguese traders at Tanegashima in 1543, which Oda Nobunaga famously deployed at the Battle of Nagashino (1575).

Three figures are typically credited with reunification:

• Oda Nobunaga, who seized Kyoto in 1568 and broke the power of militant Buddhist institutions before his death at Honnō-ji in 1582.
• Toyotomi Hideyoshi, who completed unification by 1590, conducted nationwide land surveys (the Taikō kenchi), implemented the 1588 sword hunt separating warriors from peasants, and launched two invasions of Korea (1592, 1597).
• Tokugawa Ieyasu, who won the decisive Battle of Sekigahara in 1600 and was appointed shogun in 1603.

The period also saw the arrival of Jesuit missionaries (Francis Xavier landed in 1549), expanded trade with Portugal and later the Dutch, and significant social mobility. For IR and comparative-politics purposes, Sengoku Japan is frequently studied as a case of multipolar competition, state formation through war, and the institutionalization of military government.