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September 15 to November 27, 1944Reputable source · 2 sourcesWell documented

The Battle of Peleliu becomes the war's costliest amphibious assault per capita

A four-day operation planned by Rupertus stretches into more than two months of tunnel fighting

On the timeline · around September 15 to November 27, 1944 · Allied VictoryAllied VictoryThe Battle of Peleliu becomes the war's costliest amphibious assault per capita1945

Quick facts

Location
Peleliu, Palau Islands
Dates
September 15 to November 27, 1944
Codename
Operation Stalemate II
US casualties
1st Marine Division: over 6,500, more than a third of its strength
Result
US capture after prolonged cave-fighting

What happened

Codenamed Operation Stalemate II, the invasion of Peleliu in the Palau Islands began September 15, 1944, when the 1st Marine Division landed to capture an airfield believed necessary to secure MacArthur's flank for the coming Philippines invasion. Division commander Major General William Rupertus predicted the fighting would be a quick one, telling planners it would be 'a quickie, rough, but fast,' expecting it to take three or four days. Japanese defenders of the 14th Infantry Division had abandoned the failed tactic of contesting the beaches directly and instead fought from an extensive network of caves and fortified ridges inland, a defense in depth that turned the operation into grinding, monthslong combat. The Army's 81st Infantry Division relieved the battered Marines on October 30, and organized resistance did not end until November 27, more than two months after the landing.

Why it matters

The 1st Marine Division suffered over 6,500 casualties, more than a third of its strength, in what later became known as the war's forgotten and most controversial battle, since the airfield's strategic necessity was questioned even before the fighting ended. Peleliu previewed the cave-and-tunnel defense doctrine Japan would use again, at even greater cost to attackers, on Iwo Jima and Okinawa.

How we know

Naval History and Heritage Command's official operational history documents the shift from the original Stalemate plan to the scaled-down Stalemate II, showing planners were already reassessing the operation's scope before the landing.

Sources

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The Battle of Peleliu becomes the war's costliest amphibious assault per capita · World War II · SourcedStory