The Treaty of Shimonoseki was signed on April 17, 1895, in the Japanese city that lends the treaty its name. It came into effect on May 8 that same year. According to the treaty, Taiwan belonged to Japan, but people living in Taiwan were given the opportunity to choose their nationality by either leaving or staying within two years of the treaty being signed. This ability to choose one’s own nationality is a basic human right.
In the book On Taiwan’s Status and Relations, edited by National Chengchi University history professor Hsueh Hua-yuan (薛化元), it says that the Republic of China (ROC) government announced in January 1946 that the people living in Taiwan had “regained” their status as ROC nationals, which gave rise to diplomatic protests from the UK and the US.