The CS Grenade is a non-lethal weapon which emits a yellow cloud of CS gas, commonly known as tear gas, which is used to temporary incapacitate its target without killing them. Enemies inside the gas will not be able to fire their weapons, and will be forced to move out of the gas cloud. CS gas currently does not affect Rangers, however, they will cough uncontrollably. CS grenades can be useful for escaping enemy contact in patrols without killing them, however they can also be useful for luring out enemies in defensive positions such as trenches, possibly to allow you to slip by.
CS Gas, comprised primarily of o-chlorobenzylidene malononitrile, is a non-lethal but extremely volatile airborne gas used primarily for riot control and pacification. It was discovered by two Americans, Ben Corson and Roger Stoughton, hence the nomenclature. CS gas was developed in the 1928, but still continues to be a heavily practical solution for modern SWAT teams and police strategic response.
It has been reported that thousands of tonnes of CS gas were used by the U.S. forces in Vietnam to bring Viet Cong into the open. It was also used by the North Vietnamese forces in some battles like Hue in 1968 or during the Easter Offensive in 1972. Both forces enjoyed the use of the gas in bringing enemy forces out from heavily dug-in defensive positions or from treelines or heavy brush.