The rolling barrage and carefully executed landing produced the desired effect, suppressing direct enemy fire, providing enough shock and distraction to enable the first assault waves to clear the beach and begin advancing inward. Within minutes 6,000 Marines were ashore. Many became thwarted by increasing fire over the terraces or down from the highlands, but hundreds leapt forward to maintain assault momentum. The 28th Marines on the left flank had rehearsed on similar volcanic terrain on the island of Hawaii. Now, despite increasing casualties among their company commanders and the usual disorganization of landing, elements of the regiment used their initiative to strike across the narrow neck of the peninsula. The going became progressively costly as more and more Japanese strongpoints along the base of Suribachi seemed to spring to life. Within 90 minutes of the landing, however, elements of the 1st Battalion, 28th Marines, had reached the western shore, 700 yards across from Green Beach. Iwo Jima had been severed--“like cutting off a snake’s head,” in the words of one Marine. It would represent the deepest penetration of what was becoming a very long and costly day. The other three regiments experienced difficulty leaving the black sand terraces and wheeling across towards the first airfield. The terrain was an open bowl, a shooting gallery in full view from Suribachi on the left and the rising tableland to the right. Any thoughts of a “cakewalk” quickly vanished as well-directed machine-gun fire whistled across the open ground and mortar rounds began dropping along the terraces. Despite these difficulties, the 27th Marines made good initial gains, reaching the southern and western edges of the first airfield before noon. The 23d Marines landed over Yellow Beach and sustained the brunt of the first round of Japanese combined arms fire. These troops crossed the second terrace only to be confronted by two huge concrete pillboxes, still lethal despite all the pounding. Overcoming these positions proved costly in casualties and time. More fortified positions appeared in the broken ground beyond. Colonel Walter W. Wensinger’s call for tank support could not be immediately honored because of trafficability and congestion problems on the beach. The regiment clawed its way several hundred yards towards the eastern edge of the airstrip.