Secretary of Defense Robert McNamara on the use of tear gas in South Vietnam
1965

The Federal Laboratories, a private corporation located in Salzburg, Pennsylvania, sells and distributes riot control agents worldwide. They sell and distribute the three agents with which the South Vietnamese forces are equipped; agents known as CS, CN and DM.

DM is a pepper-like irritation which causes irritation of the eyes and mucus membranes, viscous discharge from the nose, sneezing, tightness in the chest, headache, and nausea and vomiting. On the average it incapacitates from between one half hour and two hours.

CN is a tear-producing agent; it's also an irritant in the upper respiratory passages and it may cause irritations to the skin. It incapacitates on the average for approximately three minutes.

CS is a more recently developed tear-producing agent, which causes more severe irritation to the eyes, nose, and to the respiratory tract. It's usually accompanied by pains to the chest, choking and nausea. Concentrations of the agent can lead to vomiting. On the average it incapacitates for from between three to fifteen minutes.

The South Vietnamese police and their armed forces were equipped with the riot control agents starting in mid-1962. As far as we know they've been used only two or three times since then. Most recently, on January 27th of this year in an engagement in Hau Giang Province. There the communist Viet Cong took refuge in a village, using the noncombatants of the village as hostages. Rather than use firepower, thereby jeopardizing the lives of these noncombatants, the South Vietnamese forces chose to use riot control agents to drive the Viet Cong out of the area. Their objective, of course, was to save lives of the citizens and the peasants residing in the village.