Later, the South Vietnamese and Americans contested with the Viet Cong for the lower Mekong and its tributaries. With 15,600 square miles of land and more than 15,000 miles of waterways, the Mekong Delta was of vital strategic importance.

The Mekong Delta extends south and west from the city of Saigon and covers over 15,000 square miles (40,000 square kilometers). During the Vietnam War the strategic importance of the Delta was undeniable as it housed almost 8 million civilians and land movement was extremely restricted a majority of the year during the wet season.

If the struggle in the South began in order to expel the French, violence ended up transforming the countryside, and ripping Mekong Delta society apart. The delta went through two internal fractures at the beginning of the war. The first, dating from late 1945 and into 1946, split many (but not all) Khmer from Vietnamese.