Okay, so a long time ago in 1874, Japan was a big and powerful country that wanted to expand its land and power. They decided to go invade a small island called Taiwan, which was being ruled by China at the time.
Japan sent a bunch of their soldiers and ships to Taiwan, and they started to fight with the Chinese soldiers who were already there. It was a really big fight that lasted a few months, and lots of people got hurt or died.
The Japanese soldiers were really strong and had better weapons, so they eventually beat the Chinese soldiers and took over the island. After that, the Japanese made the people living in Taiwan become part of their country instead of being part of China.
It wasn't a very nice thing for Japan to do, because they hurt a lot of people and made them become part of their country without asking if they wanted to. But sometimes powerful countries do things like that to become even more powerful.