Leadup and Outbreak
In the mid-1630s, the peasants of the Shimabara Peninsula and the Amakusa Islands, dissatisfied with overtaxation and suffering from the effects of famine, revolted against their lords. This was specifically in territory ruled by two lords: Matsukura Katsuie of the Shimabara Domain, and Terasawa Katataka of the Karatsu Domain. Though the rebellion is cast by many historians as a religious uprising, this does not address the issues of the discontent from the famine and overtaxation. Those affected also included fishermen, craftsmen and merchants. As the rebellion spread, it was joined by masterless samurai who once had served families such as the Amakusa and Shiki who had once lived in the area, as well as former Arima and Konishi retainers. As such, the image of a fully "peasant" uprising is also not entirely accurate.
Shimabara was once the domain of the Arima lordly family, which had been Christian; as a result, many locals were also Christian. The Arima were moved out in 1614 and replaced by the Matsukura. The new lord, Matsukura Shigemasa, hoped to advance in the shogunate hierarchy, and so he was involved with various construction projects, including the building and expansion of Edo Castle, as well as a planned invasion of Luzon. He also built a new castle at Shimabara. As a result, he placed a greatly disproportionate tax burden on the people of his new domain, and further angered them by strictly persecuting Christianity. Even the Dutch, who had a trading post nearby and were anti-Catholic, were startled at the excessive degree of repression. These policies were continued by Shigemasa's heir, Katsuie.
The inhabitants of the Amakusa Islands, which had been part of the fief of Konishi Yukinaga, suffered the same sort of persecution at the hands the Terasawa family, which, like the Matsukura, had been moved there. Other masterless samurai in the region included former retainers of Katō Tadahiro(ja) and Sassa Narimasa, both of whom had once ruled parts of Higo Province.
Read more about this topic: Shimabara Rebellion