The American drive north continued after the 5 March standdown, but the going never got any easier. The nature of enemy fire changed--fewer big guns and rockets, less observed fire from the highlands--but now the terrain grew uglier, deteriorating into narrow, twisted gorges wreathed in sulfur mists, lethal killing zones. Marine casualties continued to mount, but gunshot wounds began to outnumber high-explosive shrapnel hits. The persistent myth among some Marine units that Japanese troops were all near-sighted and hence poor marksmen ended for good at Iwo Jima. In the close-quarters fighting among the badlands of northern Iwo Jima, Japanese riflemen dropped hundreds of advancing Marines with well-aimed shots to the head or chest. “Poor marksmen?” snorted Captain Caldwell of Company F, 1st Battalion, 26th Marines, “The Japs we faced all fired ‘Expert.’” [Illustration: _Mopping up the caves with grenades and Browning automatic rifles, Marines flush out remaining Japanese hidden in Iwo Jima’s numerous and interconnecting caves._ Department of Defense Photo (USMC) 142472 ] Supporting arms coordination grew more effective during the battle. Colonel “Buzz” Letcher established what some have identified as the first corps-level Supporting Arms Coordination Center (SACC), in which senior representatives of artillery, naval gunfire, and air support pooled their talents and resources. While Letcher lacked the manpower and communications equipment to serve as corps artillery officer and simultaneously run a full-time SACC, his efforts represented a major advancement in this difficult art. So did Colonel Vernon Megee’s Landing Force Air Support Control Unit, which worked in relative harmony with the fledgling SACC. Instances of friendly fire still occurred, perhaps inevitably on that crowded island, but positive control at the highest level did much to reduce the frequency of such accidents. In terms of response time, multiple-source coordination probably worked better at the division level and below. Most infantry battalions, for example, had nothing but praise for the Air Liaison Parties, Shore Fire Control Parties, and artillery forward observer teams which deployed with each maneuver unit. [Illustration: Marine Corps Combat Art Collection _“The Target,” by Col Charles H. Waterhouse._]