This was followed by martial law and the "White Terror" in which many thousands of people were imprisoned or executed for their political opposition to the Kuomintang. Many victims of the white terror were Taiwanese elite—political leaders, wealthier families, intellectuals, etc. In addition, mainlanders were not spared either, as many had real or perceived associations with communists before they came to Taiwan. For example, some mainlanders who had joined book clubs in mainland China, deemed leftist by the government, were liable to be arrested and many served long prison sentences for these real or perceived threats.