Role in WW2
Main article: History of Laos
In 1945 the Japanese occupied Vientiane in April. King Sīsavāngvong was detained by the Japanese, but his son Crown Prince Savāngvatthanā called on all Laotians to resist the occupiers.
Prince Phetxarāt, however, opposed this position, and thought that Lao independence could be gained by siding with the Japanese, who made him Prime Minister of Luang Phrabāng, though not of Laos as a whole. In practice the country was in chaos and Phetxarāt's government had no real authority. Another Lao group, the Lao Sēri (Free Lao), received unofficial support from the Free Thai movement in the Isan region. Thailand re-annexed a small portion of Laos following the conclusion of the French–Thai War in 1941. The territories were only returned to French sovereignty in October 1946.