Once ashore and clear of the loose sand along the beaches, the tanks, half-tracks, and armored bulldozers of the landing force ran into the strongest minefield defenses yet encountered in the Pacific War. Under General Kuribayashi’s direction, Japanese engineers had planted irregular rows of antitank mines and the now-familiar horned antiboat mines along all possible exits from both beaches. The Japanese supplemented these weapons by rigging enormous makeshift explosives from 500-pound aerial bombs, depth charges, and torpedo heads, each triggered by an accompanying pressure mine. Worse, Iwo’s loose soil retained enough metallic characteristics to render the standard mine detectors unreliable. The Marines were reduced to using their own engineers on their hands and knees out in front of the tanks, probing for mines with bayonets and wooden sticks. While the 28th Marines fought to encircle Suribachi and the beachmasters and shore party attempted to clear the wreckage from the beaches, the remaining assault units of the VAC resumed their collective assault against Airfield No. 1. In the 5th Marine Division’s zone, the relatively fresh troops of the 1st Battalion, 26th Marines, and the 3d Battalion, 27th Marines, quickly became bloodied in forcing their way across the western runways, taking heavy casualties from time-fuzed air bursts fired by Japanese dual-purpose antiaircraft guns zeroed along the exposed ground. In the adjacent 4th Division zone, the 23d Marines completed the capture of the airstrip, advancing 800 yards but sustaining high losses. [Illustration: Marine Corps Historical Collection _Marines advance warily on Airfield No. 1 towards wrecked Japanese planes in which enemy snipers are suspected of hiding. The assault quickly moved on._] Some of the bitterest fighting in the initial phase of the landing continued to occur along the high ground above the Rock Quarry on the right flank. Here the 25th Marines, reinforced by the 1st Battalion, 24th Marines, engaged in literally the fight of its life. The Marines found the landscape, and the Japanese embedded in it, unreal: There was no cover from enemy fire. Japs dug in reinforced concrete pillboxes laid down interlocking bands of fire that cut whole companies to ribbons. Camouflage hid all enemy positions. The high ground on either side was honeycombed with layer after layer of Jap emplacements.... Their observation was perfect; whenever a Marine made a move, the Japs would smother the area in a murderous blanket of fire. The second day of the battle had proven unsatisfactory on virtually every front. To cap off the frustration, when the 1st Battalion, 24th Marines, finally managed a breakthrough along the cliffs late in the day their only reward was two back-to-back cases of “friendly fire.” An American air strike inflicted 11 casualties; misguided salvos from an unidentified gunfire support ship took down 90 more. Nothing seemed to be going right.