Admiral Nimitz’ Central Pacific Fleet was like a spear driving straight into gut of the Japanese Empire. While MacArthur aimed at the Philippines for his return, Nimitz was cutting across the axis. His next targets were the critical Marianna’s Islands, which included Guam, Tinian and Saipan. These were the first islands in the Japanese “Inner Defense Ring” and the Japanese planned to make a fight of it. The Americans had to be stopped.
On 15 June, 1944 Lieutenant General Howland “Howling Mad” Smith’s 2nd and 4th Marine Divisions and US Army 27th Infantry Dvision, stormed ashore on Saipan, through lanes cleared of obstacles by the first use of UDTs or Underwater Demolitions Teams (forerunners of the SEALS), and met three times as many Japanese as Naval Intelligence predicted. And they also met everything left in the Japanese navy that could float or fly.
The Americans knew the Marianna’s were important, but only the Japanese truly knew how critical they were. First, they both knew Allied planes flying from the Marianna’s would effectively cut off all Japanese possessions to the west and south: Indonesia, the Philippines, Singapore, Java, Borneo, Malaysia, and New Guinea. Supplies would not get south, and raw materials would not go north. Allied wolfpacks were already wreaking havoc with Japanese shipping, if they were directed by reconnaissance planes from Saipan, they would be devastating. Also, they both knew American bombers from the Marianna’s would be in range to bomb the Japanese home islands. This would be even more alarming once the Japanese discovered a new Allied weapon, first used on Saipan, which would be catastrophic to Japan’s wooden cities: napalm. Finally, most importantly and unbeknownst to the Americans, the Imperial Japanese High Command had been lying to the people for years regarding the conduct of the war. The people and most of the government of Japan thought the war was being won. Their propaganda machine would not be able to hide the loss of Saipan, a prewar Japanese territory, nor the clouds of B-29s that were sure follow. They would have to admit they were losing the war.
The Marianna’s Islands were extensively reinforced, particularly Saipan. The Japanese planned on fighting for the whole island from the surf to the last dug in bunker, effectively combining the old and new defensive techniques. Also, two of the Japanese’ best commanders were in charge of the island, through under different circumstances. Lieutenant General Yoshitsugu Saito was one of the army’s best and was hand-picked to lead the defense of the first prewar Japanese territory to see invasion. His navy counterpart, Vice Admiral Nagumo, the victor of Pearl Harbor and easily the Japanese’ best carrier admiral, was there in disgrace, commanding the island’s cruiser and destroyer defense flotilla for losing the battle of Midway. (He influenced the battle on land but had no effect on the wider naval battle in the Marianna’s, although he was sorely needed.) Finally, the cream of what was left of the Japanese Navy was committed to the defense of the islands.
For the next three weeks, the fighting on Saipan was fierce but the issue was never in doubt. The inter-service political battles between the US Army and the US Marines that erupted because of the fighting would eventually garner more attention. The Japanese finally got their Kantai Kessen, decisive battle, with the US Navy in the Philippine Sea, but were soundly annihilated by Allied quality, quantity and professionalism. By the beginning of July, Japanese naval airpower was destroyed, never to return. The first recon planes were spotting for the submarines before the fighting was completed, and the first B-29s arrived soon after. In a glimpse of what was to come, most of the Japanese civilians on the island committed suicide by jumping off the southern cliffs, to the horror of the watching US soldiers and marines.
With the loss of Saipan, the Japanese government began preparing the Japanese people for the worst: the invasion of the Home Islands. To the Americans the turning point of the War in the Pacific was Midway and Guadalcanal. To the Japanese, it was Saipan.