On June 4, the Korean king, Gojong, requested aid from the Qing government in suppressing the Donghak Rebellion. Although the rebellion was not as serious as it initially seemed and hence Qing reinforcements were not necessary, the Qing government still sent the General Yuan Shikai as its plenipotentiary to lead 2,800 troops to Korea.
According to the Japanese, the Qing government had violated the Convention of Tientsin by not informing the Japanese government of its decision to send troops, but the Qing claimed that Japan had approved this. The Japanese countered by sending an 8,000-troop expeditionary force (the Oshima Composite Brigade) to Korea. The first 400 troops arrived on June 9 en route to Seoul, and 3,000 landed at Incheon on June 12.
Japanese foreign minister Mutsu Munemitsu meets with Wang Fengzao, the Qing ambassador to Japan, to discuss the future status of Korea. Wang states that the Qing government intends to pull out of Korea after the rebellion has been suppressed and expects Japan to do the same. However, China retains a resident to look after Chinese primacy in Korea.
Additional Japanese troops arrive in Korea. Japanese prime minister Itō Hirobumi tells Matsukata Masayoshi that since the Qing Empire appear to be making military preparations, there is probably "no policy but to go to war". Mutsu tells Ōtori to press the Korean government on the Japanese demands.
In early June 1894, the 8,000 Japanese troops captured the Korean king Gojong, occupied the Gyeongbokgung in Seoul and, by June 25, replaced the existing Korean government with members of the pro-Japanese faction.