In the 1960s, the U.S. Army adopted the M72 LAW rocket, a lightweight, collapsible rocket launcher with the ability to penetrate moderate thicknesses of enemy armor. During the Vietnam War, the weapon was used primarily against NVA and Viet Cong defensive works and emplacements, as there were few encounters against enemy armor. Overall, the LAW was regarded as a success, though its ignition system frequently suffered from misfires in the heat and humidity of Vietnamese jungles. The LAW has since been replaced by the AT4 (M136).