The Battle of Ko Chang took place on 17 January 1941 during the Franco-Thai War in which a flotilla of French warships attacked a smaller force of Thai vessels, including a coastal defence ship. The battle resulted in a tactical victory by the French Navy over the Royal Thai Navy although the strategic result is disputed. The Japanese intervened diplomatically and mediated a ceasefire which was in Thailand's favor as all disputed territories in French Indochina were ceded by Vichy France to Thailand. In the end, two Thai ships were sunk and one was heavily damaged. Within a month of the engagement, the French and the Thais negotiated a peace which ended the war.