On 30 March 1972 the South Vietnamese positions along the Demilitarized Zone (DMZ) that separated the North from South Vietnam were suddenly shelled by hundreds of heavy guns and multiple rocket launchers. Caught in a series of outposts of what was the former 'McNamara Line', the shocked defenders had just enough time to emerge from their bunkers at the end of the barrage before they were attacked by regular North Vietnamese Army divisions, supported...