The Sinmiyangyo, often referred to as the Second Korean Expedition, was a significant military operation undertaken by the United States in 1871. Under the command of Captain McLane Tilton, a contingent of 109 Marines launched a naval assault on the Han River forts situated on Kanghwa Island, which was part of Korea. This operation was initiated in response to the Korean government's refusal to establish diplomatic relations with the U.S. and the expulsion of an American ship, the General Sherman, from Korean waters in the late 1860s. The American forces aimed to demonstrate their military capabilities and compel the Korean government to open ports to foreign trade.The attack was executed with coordination between naval and land forces. The Marines landed on the island where they faced resistance from Korean soldiers defending the forts. Despite suffering casualties, the U.S. forces successfully captured the forts, showcasing their naval superiority. The skirmishes marked one of the few direct engagements between the U.S. military and Korean troops during this period. Following the conflict, diplomatic negotiations were attempted, but initial hostility persisted in U.S.-Korea relations for several more years before any lasting agreements were established.