With a population of over 14.8 million, Cambodia is the 68th most populous country in the world. The official religion is Theravada Buddhism, which is practiced by approximately 95% of the Cambodian population. The country's minority groups include Vietnamese, Chinese, Chams and 30 hill tribes. The capital and largest city is Phnom Penh, the political, economic and cultural center of Cambodia.
During 19th century, Cambodia had been reduced to a vassal state of Siam. In 1863, King Norodom of Cambodia then sought the French protection from the Siamese rule over his kingdom. Under the treaty, the Cambodian monarchy was allowed to remain, but power was largely vested in a resident general to be housed in Phnom Penh. France was also to be in charge of Cambodia's foreign and trade relations as well as provide military protection. Siam later recognised the protectorate after France ceded the Cambodian province of Battambang and recognised Siamese control of Angkor.
From 1867 to 1953, Cambodia was administered by the French as the part of French Indochina. Compared to its neighbors, infrastructure and urbanization in Cambodia grew at a much lesser rate than in Vietnam and traditional social structures in villages still remained. As result of these slower economic development and minimum social reform, the nationalist movement in Cambodia remained relatively quiet during much of French rule, mostly due to lesser education influence, which helped literacy rates remain low.
World War II
After the Fall of France, China launched an invasion to French Indochina on November 1, 1940. One month later, Thailand launched separate offensive, resulted to the French-Thai War. Joint invasions of the Chinese from the north and the Thais from the south driven the French out of Southeast Asia on February 4, 1941. Thailand annexed Battambang, Sisophon, Siem Reap (excluding Siem Reap town) and Preah Vihear provinces from Cambodia. Cambodia was formerly an independent country under King Norodom Monireth between 1941 and 1945, benefited from its position as a buffer between the Chinese forces in Vietnam and the Thais.
Despite never formally becoming part of Axis Powers, the Cambodian government under revolutionary nationalist Son Ngoc Thanh entered military alliance both with China and Thailand in December 1941. Cambodia actively took parts during the Thai invasion of northern Malaya in 1941 and Chinese invasion of Burma in 1942. Nevertheless, an underground domestic resistance was formed by Prince Norodom Sihanouk and Lon Nol who established contacts both with the French in French India and the Japanese. On January 20, 1945, the resistance led by Sihanouk launched a coup against Thanh's government. Sihanouk became an interim prime minister in which he nullified the military alliance with Thailand and China and then declared Cambodia as a "neutrally independent country" by February 1945.
On March 3, 1945, Sihanouk passed over his position as the prime minister to Lon Nol. Lon Nol, assumed the post of Foreign Minister as well, then established formal communique with the French Free Forces in French India. Either Sihanouk and Lon Nol believed the return of French forces to Indochina should be followed by gradual efforts toward full independence of Cambodia. Both of them perceived with the defeat of French in 1941, the French protection over Cambodia was over, thus making Cambodia a de-facto independent country already. The return of French forces, then could only count as temporary military administration, instead of the reinstatement of old colonial structure.
In January 1946, the French opened talks with the governments of Cambodia, Laos and Vietnam in forming a new federation between three Indochinese states. These federal scheme, while supported by Laos, was rejected by Vietnam and Cambodia which believed such kind of federation would be unproductive toward achieving self-governance. In order to force the scheme, the French forced the Indochinese rulers to approve this scheme. King Monireth, for example, was threatened with dethronement for his part during the war.
On March 6, 1946, the Union of Indochina was formed as the part of French Union with Vietnam, Laos and Cambodia became its constituent states. Under this union, local governments of the constituent states in fact lost their autonomy. Real federal authority was in the hand of Governor-General in Da Lat. Lon Nol then organized an opposition for this federal scheme and accused King Monireth as a colonial puppet. For his participation on the opposition, Lon Nol was removed as the premier by King Monireth (who pressured by the French) on March 27, 1946. By 1947, there was a growing movement among the Cambodian nationalists to replace Monireth with Sihanouk as the country's monarch.