Chambers commanded the 3rd Battalion, 25th Marines in the Iwo Jima landing on February 19, 1945. His sector was beneath high ground from which heavy enemy fire raked the whole landing beach. "Capture of the high ground," the Medal of Honor recommendation stated, "... was essential to the success of the D-Day operations. It is an established fact that had it not been done, it would have constituted a most serious threat to the subsequent operations of the 5th Amphibious Corps."