Ever since its establishment after the Chinese Civil War, the PRC has claimed the territories governed by the Republic of China (ROC), a separate political entity today commonly known as Taiwan, as a part of its territory. It regards the island of Taiwan as its Taiwan Province, Kinmen and Matsu as a part of Fujian Province and islands the ROC controls in the South China Sea as a part of Hainan Province and Guangdong Province. These claims are controversial because of the complicated Cross-Strait relations, with the PRC treating the One-China policy as one of its most important diplomatic principles.