Major General William Rupertus promised his commanders that a six-square-mile coral island would be secured in four days. Instead, Operation Stalemate II, the Battle of Peleliu, became a 73-day fight with the highest casualty rate of any amphibious operation in the Pacific war. This episode sets the strategic stage in 1944, with MacArthur and Nimitz split over the Philippines versus Formosa until President Roosevelt mediated at Pearl Harbor, and explains how Peleliu's airfield became a flank-protection chore for MacArthur's return rather than a real objective.

What the planners missed was Colonel Kunio Nakagawa's new defense-in-depth doctrine. Rather than contesting the beaches with banzai charges, his engineers turned Umurbrogol Mountain into a honeycomb of over 500 caves with sliding armored doors and slanted entrances, then held their fi ...