The French expedition to Korea (French: Expédition française en Corée, Korean: 병인양요) was an 1866 punitive expedition undertaken by the Second French Empire against Joseon Korea in retaliation for the execution of seven French Catholic missionaries. The encounter over Ganghwa Island lasted nearly six weeks. The result was an eventual French retreat, and a check on French influence in the region. The encounter also confirmed Korea in its isolationism for another decade, until Japan forced it to open up to trade in 1876 through the Treaty of Ganghwa. In contemporary South Korea it is known as the Byeong-in yangyo, or "Western disturbance of the byeong-in year".

French expedition to Korea - Wikipedia