In 1859, the Khmer Krom of the province of Srok Khleang, under command of Sena Sous, stood up to the Vietnamese in the battles of Mahatup and Chong Ballang. During three years of fighting the Khmer Krom won most military engagements in the areas surrounding the province. Unfortunately A Vietnamese undercover agent, belonging to other ethnic group, had infiltrated his rank joined the Khmer force and became Sena Suos’s most trusted chief. Later, Sena Sous was poisoned by the man (his name was unknown).