at noon on 30 march 1972, 30,000 pavn troops, supported by regiments of tanks and artillery, rolled southward across the demilitarized zone (dmz) that separated the two vietnams. this three-division force caught the army of the republic of vietnam (arvn) and their american allies unprepared. the pavn force struck the defensive positions of the arvn 3rd division and threw it into disarray. south vietnamese forces then fell back, and a race began between both belligerents to the bridges at đông hà and cam lộ.