In 1894, the DongHak rebellion threatened to topple the Korean government. Fearing this, the Korean government asked the Chinese to aid them in putting down the rebellion. Although the Chinese moved some troops into Korea, the Korean government ended the rebellion alone. 

The Japanese were upset that the Chinese moved into Korea, so they followed suit and invaded Korea. The Japanese assassinated the Queen of Korea, and then defeated the Qing military in Korea. Japan went on to claim Korea as a colony, conquer large swaths of Asia, and were only defeated after World War 2.