Thailand was nominally an ally of Japan at the beginning of the war. Field Marshal Plaek Phibunsongkhram, a military dictator with nationalist leanings, ruled the country under the nominal rule of King Rama VIII, who was just fourteen years old in 1939 and remained in Switzerland until the war ended. Thailand remained uninvolved when war broke out in Europe, but it took the opportunity of France's defeat to settle claims to parts of French Indochina, in the Franco–Thai War. The December 1941 Japanese invasion of Thailand brought five hours of war after which Phibun surrendered and acquiesced, making the country a stepping-stone to open the Burma Campaign.