The Shimabara Rebellion (島原の乱) was an uprising that occurred in the Shimabara Domain of the Tokugawa Shogunate in Japan from 17 December 1637 to 15 April 1638.

Matsukura Katsuie, the daimyō of the Shimabara Domain, enforced unpopular policies set by his father Matsukura Shigemasa that drastically raised taxes to construct the new Shimabara Castle and violently prohibited Christianity. In December 1637, an alliance of local rōnin and mostly Catholic peasants led by Amakusa Shirō rebelled against the Tokugawa shogunate due to discontent over Katsuie's policies. The Tokugawa Shogunate sent a force of over 125,000 troops supported by the Dutch to suppress the rebels and defeated them after a lengthy siege against their stronghold at Hara Castle in Minamishimabara.

Following the successful suppression of the rebellion, Shirō and an estimated 37,000 rebels and sympathizers were executed by beheading, and the Portuguese traders suspected of helping them were expelled from Japan. Katsuie was investigated for misruling, and was eventually beheaded in Edo, becoming the only daimyō to be executed during the Edo period. The Shimabara Domain was given to Kōriki Tadafusa. Japan's policies of national seclusion and persecution of Christianity were tightened until the Bakumatsu in the 1850s.

The Shimabara Rebellion was the largest civil conflict in Japan during the Edo period, and was one of only a handful of instances of serious unrest during the relatively peaceful period of the Tokugawa shogunate's rule... read more on Wikipedia

Source: Wikipedia