Moran, Jim Images of War. Battle of Peleliu, 1944. Three Days That Turned Into Three Months

After the Allies had defeated the Japanese in the Solomons and the Dutch East Indies, the capture of the Philippines became General MacArthur's next objective. For this offensive to succeed, MacArthur felt compelled to secure his eastern flank by seizing control of the Palau Islands, one of which was Peleliu. The task of capturing this island, and the enemy airfield on it, was initially handed to Admiral Nimitz.
The Palau Islands, however, formed part of Japan's second defensive line, and Peleliu's garrison amounted to more than 10000 men. Consequently, when the US preliminary bombardment began on 12 September 1944, it was devastating. For two days the island was pounded relentlessly. Such was the scale of the destruction that the commander of the 1st Marine Division, Major General William H. Rupertus, told his men: "We're going to have some casualties, but let me assure you this is going to be a fast one, rough but fast. We'll be through in three days - it may only take two".
At 08:32 hours on 15 September 1944, the Marines went ashore. Despite bitter fighting, and a ferocious Japanese defence, by the end of the day the Marines had a firm hold on Peleliu. But rather than Japanese resistance crumbling during the following days as had been expected, it stiffened, as they withdrew to their prepared defensive positions. The woods, swamps, caves and mountains inland had been turned into a veritable fortress - it was there where the real battle for possession of Peleliu was fought.
Day after day the Americans battled forward, gradually wresting control of Peleliu from the Japanese. Despite Major General Rupertus' prediction, it was not until 27 November, after two months, one week and five days of appalling fighting, and a final, futile last sacrificial charge by the remaining enemy troops, that the Battle of Peleliu came to an end.

In the swamps of the island and in their well-developed mountain and tunnel fortresses, the Japanese defenders put up unprecedented resistance to the US Marines.