In the remaining years of the Second Indochina War, Nguyễn Thanh Châu spent most of his time in Tây Ninh Province of the Mekong Delta’s Plain of Reeds (Đồng Tháp Mười) alongside artists Thái Hà, Huỳnh Phương Đông and Lê Lâm. He witnessed battles in places such as the Tiền River, the Black Virgin Mountain Range (Núi Bà Đen) and near the tunnels of Củ Chi before his advance with the army on its final assault on Saigon in April 1975 and the city’s liberation.
Châu made many drawings during his time with the People’s Liberation Armed Forces of South Vietnam (PLAF) and National Liberation Front (NLF). Usually, he would make a quick pencil sketch directly on the battlefield on crôky paper (sketching paper), which he then painted with watercolours at a later stage. Art materials were supplied by the Soviet Union and redistributed by the Democratic Republic of Vietnam (DRV) government to resistance artists working in the south. Every month or two,
Châu would take his sketches to the central military base in Tây Ninh, where he could safely complete the drawings. Occasionally, he would use a camera from Czechoslovakia to take pictures of his surroundings for additional documentation in order to help him complete his pencil sketches. However, this was limited due to the fear that photographs could reveal secret locations.
His excursions with PLAF guerrillas in the Mekong Delta brought him as close to the conflict as possible, giving him access to guerillas in the Forest of “Assassins”, hideouts in the mangrove forests of the Mekong Delta, NLF flag makers in Tiền Giang Province, scenes of serenity and the final assault on Saigon.

At an undisclosed location, Châu’s watercolour sketch of guerrilla’s armed with a rocket propelled grenade (fig. 1) was most likely rendered in the Mekong Delta considering his movements in 1973. When describing the image in interviews conducted in 2010 and 2011, Châu recognised the two soldiers as part of the B40 gun encampment. The two soldiers were firing on US helicopters conducting an air raid by day.