From the 1860s France began establishing a presence in the region, initially in modern Cambodia and Vietnam, and the colony of French Indochina was created in 1887. The Lao kingdoms were at this point tributary states of the Kingdom of Siam (the old name for Thailand), however all areas east of the Mekong were annexed to French Indochina in 1893 following the Franco-Siamese War. In 1902 Siam was forced to cede areas west of the Mekong to France, encompassing the modern province of Sainyabuli and the western half of Champasak Province. More land was ceded in another treaty in 1904, and again in 1907. A minor treaty in 1926 cleared up the outstanding issue of sovereignty over islets in the Mekong. Following Japan’s invasion of French Indochina in 1940 the ceded areas west of the Mekong and south-western Laos were returned to Thailand, however this arrangement was annulled following Japan's defeat and the pre-war border reinstated.