Chhuon was born in Siem Reap and grew up in Prey Veng, joining the French militia in which he rose to the rank of sergeant.
[3] In August 1946 a disparate group of activists led by Chhuon, Prince Norodom Chantaraingsey and the leftist Son Ngoc Minh fought French troops in Siem Reap over the course of several days.
However, in late 1949 he and his men went over to the French, who rewarded him with virtual control of parts of northern Cambodia and an official military post as commander of the "Franco-Khmer Corps".
They accredited him with powers of invulnerability, reinforced by his habit of demonstrating feats of strength and his "daunting" appearance, being cadaverously thin with "unblinking, deep-set eyes".
Although he had begun his career fighting alongside the Viet Minh, Chhuon's increasingly strident anti-communism caused him to be suggested by Robert McClintock, the US Ambassador to Cambodia between 1954 and 1956, to cultivate as a possible replacement for Sihanouk.