We did a 2-tank dive off Peleliu Island, and then got dropped off to take a WWII tour with a local guide. There are Japanese and US memorials on the island and tanks, zero fighters, guns and pillboxes still remain. 
Brief History:
MacArthur’s controversial decision to invade Palau in Sept 1942 had questionable (if any) strategic value. Codenamed ‘Operation Stalemate’, US forces were expected to secure Peleliu's airstrip within 3 days but the battle lasted almost 3 months.
The Japanese had militarized old mining caverns, creating bunkers for artillery and machine guns with steel doors and slanted entrances to repel flame-throwers & grenades. These caves were connected through a vast system allowing the Japanese to evacuate and reoccupy the positions as necessary. 
It was very spooky crawling through these tunnels and the majority of locals will not go into the caves as they fear the ghosts of the soldiers.When the battle was finally over, the American marines and Infantary divsion had suffered 10,000 casualties. Only 18 Japanese soldiers out of the 11,000 strong garrison surrendered – the rest had fought to the death.
The guide told us that two years after the war had ended, 38 Japanese soldiers walked out of a cave and surrendered to American officers. The last survivor was finally captured in 1957!
