The crisis had been building for weeks. In June 1894, the Donghak Peasant Rebellion had forced the Korean government to request Chinese military assistance, even though the rebels had already agreed to a ceasefire. China dispatched roughly 2,800 soldiers to the harbor at Asan, about 70 kilometers from Seoul. Japan, closely watching events on the peninsula, immediately sent its own forces -- first 420 sailors to Seoul as a counterbalance, then approximately 8,000 soldiers of the Oshima Composite Brigade to the port at Chemulpo and onward to Yongsan. Japanese officials publicly denied any intention to intervene, lulling the Qing viceroy Li Hongzhang into believing war was not coming. Behind closed doors, Japan demanded that Korea sever its relationship with China, establish military infrastructure for Japanese use, and begin reforms under Japanese guidance. The Korean government refused and demanded both foreign armies leave.

The Japanese approached Gojong's father, the Heungseon Daewongun, who had been living under house arrest imposed by the king. He was a political rival of the queen and amenable to cooperation, but extracted a promise: "Japan will not demand a single piece of Korean territory if the reforms succeed." With the Daewongun secured, the assault began at dawn. The 2nd Battalion breached Yeongchumun Gate at 5 am. Simultaneously, the 1st Battalion broke through Sinmumun and Gwanghwamun, destroying Geonchunmun gate with explosives. Japanese soldiers forced the Royal Escort Palace Guards and Mounted Guard Infantry behind the pine trees and palace walls flanking Gwanghwamun, cutting them off from reinforcement. Outgunned and outnumbered, the Korean guards were overwhelmed. Commander Yamaguchi and his men swept through the east and west wings, converging on the Hamhwadang residence where King Gojong sheltered.

Yamaguchi arrived at Hamhwadang with his sword drawn, claiming he had come to protect the king. At 7:30 am, Gojong commanded his guards to stop fighting. The last defenders at Yeongchumun surrendered thirty minutes later. But the battle was not over. At around 3 pm, the Metropolitan Guards near Dongdaemun engaged the Japanese 11th Regiment in a fierce firefight that lasted until the Japanese flanked them at 5 pm. Palace Guards in the outskirts of the city mobilized artillery, police, and cavalry to surround the palace, but a Korean collaborator forged an order in the king's name commanding all units to lay down their weapons. On July 25, Gojong was forced to formally surrender political control to his father, who now ruled in consultation with the Japanese. The existing government was dissolved and replaced with a pro-Japanese administration under Prime Minister Kim Hong-jip.

The new government's first acts were to disband the Capital Guards, demand the expulsion of Chinese forces, and request additional Japanese troops. China rejected the puppet government, and Japan used this as pretext to attack the Qing forces still encamped at Asan. The Battle of Seonghwan followed, the opening engagement of the First Sino-Japanese War. Japan won the battle, won the war, and in 1895 forced China to sign the Treaty of Shimonoseki, which compelled the Qing to recognize "the complete independence and autonomy of Korea." The irony was bitter: Korea's independence from Chinese suzerainty had been purchased by Japanese force, and that force was never going to leave voluntarily. Within a year, the Daewongun proved unmanageable, the reform cabinet was sidelined, and Japan's attention shifted to more direct forms of control -- culminating in the assassination of Queen Min inside this same palace in October 1895.