Despite European pressure, Thailand is the only Southeast Asian nation that has never been colonized.[22] This has been ascribed to the long succession of able rulers in the past four centuries who exploited the rivalry and tension between French Indochina and the British Empire. As a result, the country remained a buffer state between parts of Southeast Asia that were colonized by the two colonizing powers, Great Britain and France. Western influence nevertheless led to many reforms in the 19th century and major concessions, most notably being the loss of a large territory on the east side of the Mekong to the French and the step-by-step absorption by Britain of the Malay Peninsula