During that late 19th-century feeding frenzy known as colonial expansion, one of the most dramatic sites was what was then called Indochina. There was great rivalry between British imperialism and French colonial ambitions, particularly in upper Laos. There, the several small states that had been able to preserve their relative independence by paying tribute to all the surrounding regional powers were finally subjugated.
A 1893 gunboat incident gave the French the pretext needed to take these territories from Siam and establish suzerainty. Formerly neutral states such as those of the Muong Sing and the Sip Song Pana thus disappeared to become part of Indochina — present-day Laos and part of neighboring Vietnam.
Secure in their victory, the French organized something called the Mission Pavie, a series of official excursions into the interior that surveyed the ground and drew up maps, especially those of the disputed borders between Laos, Siam, Cambodia, Yunnan and Vietnam. The Mission published a series of reports, volumes in which their accomplishments were recorded.