Career
He served as the inspector in the Hoeryung region in 1866 and he led the defense of Ganghwa Island during in 1871. When the American Asiatic Rose"s Squadron arrived at coast of the island in 1871, the royal council appointed Eo to serve as the Commandant. He was posthumously appointed the Minister of War.
During the war, Eo Jae-yeon"s flag, "Sujagi" was taken by American Squadron.
On June 10, 1871, five American warships departed from Nagasaki, Japan to Ganghwa Island, bringing about 1,230 Marines and 85 cannons. The fundamental aim of the expedition was not a full-scale war, but gunboat diplomacy.
About 240 Joseon soldiers were killed, 100 were drowned, and 20 were captured, while three United States troops were killed and six were injured.