This photo of a March 1966 North Vietnamese Army training exercise shows the NVA’s primary infantry weapons: in the background, the 7.62 mm AK-47, renowned for its reliability even in adverse conditions; in foreground, the 7.62 mm Degtyaryov RPD squad machine gun, lighter than the M60 but lacking the ability to change barrels when it overheated. (AP Photo/North Vietnamese News Agency)