When American military planners began searching for islands they could use to attack Japan from, they identified the Marianas island chain as a perfect location. One of these, the island of Saipan, was very well-defended and also contained a Japanese civilian population. The subsequent battle proved to be a grueling fight that set the stage for Americas air campaign against Japan.Saipan Under Japanese ControlJapanese Governors residence in Garapan, Saipan, Date Unknown. Source: National Diet Library, JapanIn 1914 during the First World War, the Japanese Empire took control of several islands in the Marianas island chain from Germany. The archipelago had previously been colonized by Spain for several centuries. Japan hoped to expand its burgeoning empire and Saipan, the largest island in the Marianas, provided a useful link to the rest of the Pacific. In 1919, Japan was formally granted permission to govern the island by the League of Nations as part of the South Seas Mandate.Japan saw the island as a major hub of sugar production and overseas trade. It also hoped to encourage the settlement of Japanese people in the territory. Japanese businessmen built major sugar plantations, using cheap labor from the native Chamoru (Chamorro) community. The main city of Garapan started to resemble Tokyo and Japanese cultural customs and norms started to take hold on the island. Tens of thousands of Japanese, attracted by the promise of cheap land and business opportunities, moved to Saipan in the 1920s and 1930s.Japans administration of the South Seas Mandate was predominantly civilian for the interwar period until Japans military started to take control of the Ministry of Colonial Affairs. Initially, Japanese rule was benevolent in that it focused on building the islands economy and infrastructure. However, the onset of WWII meant that repression became more intense, especially against the Chamoru people. The increase of Japanese soldiers and sailors taxed the islands resources and led to more pressure on the islands civilian population.The Plan to Take the IslandsAdmirals Ernest King, Chester Nimitz, and Raymond Spruance on the deck of the USS Indianapolis, 1944. Source: US Naval History and Heritage CommandAmerican military commanders held different opinions on how best to expel the Japanese from the Pacific. Many American generals, such as General Douglas MacArthur, hoped to advance from the south by retaking the Philippines, New Guinea, and the Solomon islands. Others, such as US Pacific Fleet Admiral Chester Nimitz, believed that the best way forward was an offensive through the Central Pacific relying on American naval superiority to gain control of islands that could be used as a springboard to attack Japan directly. In the end, the US government had the military capacity to pursue both courses of action.Before the American entry into the war, US planners had come up with War Plan Orange. This entailed a major strike into the Central Pacific, including Saipan. Admiral Nimitz, with the support of Chief of Naval Operations Admiral Ernest King, began allocating resources for a joint attack on the Japanese garrisons in the Marianas. Several divisions would assault Saipan, Tinian, and Guam with the aim of taking over the airfields on all three islands and destroying the Japanese garrisons. The Pacific Fleet would provide major naval assets to help with the landings and keep the Japanese fleet away.The US Navy was a major force behind the inclusion of Saipan as a target. At the Quebec, Casablanca, and Cairo Conferences, Admiral King pushed Allied leadership to support attacking the Marianas. The introduction of the B-29 bomber helped because they had the range to reach Japan from the Marianas.Opposing ForcesA Marine training in Hawaii before the invasion of Saipan, 1944. Source: imagesofoldhawaii.comOperation Forager, the name of the operation to take Saipan, involved one of the strongest expeditionary forces the Americans employed up to that point in the Pacific. The 2nd and 4th Marine Divisions, both formations with extensive experience, were assigned to spearhead the assault. They formed the V Amphibious Corps, one of two Marine corps-sized headquarters formed in WWII, under the command of Lieutenant General Holland Smith.A very aggressive commander, Smith aimed to land his forces on a set of beaches in Saipans southwest and drive towards the east and north. The 27th Infantry Division was placed in reserve to reinforce either the Guam or Saipan landing forces. These three divisions were backed by a formidable array of weapons including hundreds of artillery pieces and 150 tanks.At sea, the navy assembled a force of several hundred ships including warships and transport vessels. The Fifth Fleet, commanded by Admiral Raymond Spruance, was assigned to cover the Saipan and Guam landings concurrently. Its strongest component was Task Force 58, led by Admiral Marc Mitscher, which contained 15 fleet carriers with hundreds of planes. The Navy was prepared for three possible Japanese counterattacks: submarine attacks on convoys, air raids on the fleet, and a sortie by Japans Combined Fleet.Painting of the Japanese Kido Butai (Date Unknown)In 1944, Japans leaders considered the Marianas island chain to be a pivotal part of the defense of the empire. They knew that the Americans wanted control of the airfields in the region and feared what could happen if the islands were lost. Accordingly, Prime Minister Hideki Tojo ordered the islands reinforced and defended to the last man.On land, the Japanese contingent on Saipan was larger than what American planners had anticipated. The 31st Army was headquartered on Saipan, although its commander was absent during the battle. General Yoshitsugu Saito was the senior army commander and his 43rd Infantry Division was the main element of the garrison. He also had the 47th Independent Mixed Brigade and several ad-hoc battalions of sailors from ships docked at the island. Most defenses were set up on the beach to stop the Americans at the waters edge.The garrison knew that its only hope for victory was if the Navy could come to its rescue. Vice-Admiral Soemu Toyoda, commander of the main Japanese naval force, the Combined Fleet, created a plan to strike the Fifth Fleet in the Philippine Sea. This would involve massive air attacks by hundreds of planes. The core of this fleet was the main force of carriers, known as the Kido Butai. Toyoda, Saito, and other officials in Tokyo believed that if American losses were high enough, they would be forced to sign a peace deal advantageous to Tokyo.The Other D-DayMarines from the first wave bogged down under Japanese fire from behind the beaches, 1944. Source: World War II TodayA mere nine days after the Overlord landings in France, the Fifth Fleets landing force under Rear-Admiral Kelly Turner began pounding the landing zones. Marine units landed on several beaches in southwest Saipan at 8:40 a.m. The 2nd Marine Division had two regiments land abreast on Red and Green beaches while the 4th seized Blue and Yellow beaches. Japanese fire flailed the beaches and inflicted very heavy losses. Dozens of artillery pieces emplaced on the high ground inland fired at the navy landing craft. They were assisted by ranging flags placed by the garrison before the landing and as many as 40% of the landing craft were hit.An attempt to draw the Japanese away from the beaches by feinting landing craft northward proved unsuccessful. The reefs also made disembarkation difficult. Nonetheless, the Marines pushed forward and began clearing pillboxes and trenchlines. By the end of the day, Marine units broke through the 43rd Divisions battalions in the sector and established a foothold several miles deep. Reserve units pushed ashore under naval covering fire and heavier equipment, such as artillery and bulldozers, began to arrive.Japanese forces were committed to retaking the area and driving the Americans back into the sea. General Saito ordered several counterattacks during the night with elements of the 9th Tank and 136th Infantry regiments. These attacks were disorganized and bogged down under heavy fire and failed to accomplish any of Saitos objectives. As a result, the Americans were in a good position to continue their offensive towards the airfields.Pushing InlandJapanese tanks knocked out during Saitos counteroffensive, 1944. Source: The Armory LifeThe heavy losses sustained by the Marines during the landings compelled General Smith to commit his reserves earlier than planned. The remaining Marine regiments were landed and on the 16th, the first two regiments of the 27th Infantry Division landed. The division did not have the stellar combat pedigree of the 2nd and 4th Marine Divisions. Its prior battle on Makin was badly managed and General Smith was very critical of its performance.As the Marines and GIs began consolidating their gains, General Saito decided to continue his counterattacks. 35 tanks from the 9th Tank Regiment along with infantry from the 136th Infantry Regiment launched an attack intending to split the two Marine divisions. The attack again failed because of poor coordination and the lack of support from Japanese marine units around the beach.Repeated counterattacks squandered Saitos strength, enabling the Americans to push further inland. Within the next several days, they seized the area of Lake Susupe and closed in on Aslito Airfield. While the 2nd Marine Division began pivoting northward towards the town of Garapan and Mount Tapochau, the 4th Marine Division and 27th Infantry Division advanced onto the airfield and cut off the Japanese forces in the south from the main element in the north. The 27th sent a regiment to destroy the lone Japanese battalion guarding Nafutan Point in the south and the remaining forces began the main push north after June 20.The Marianas Turkey ShootJapanese plane shot down near an unidentified US carrier during the Battle of the Philippine Sea, 1944. Source: The American AlmanackWhile the fighting raged on the island, the US and Japanese navies were posturing before the biggest carrier battle in history to date. Admiral Toyoda insisted that the Combined Fleet sail regardless of the risks and the fact that most land-based Japanese planes had been destroyed before the landings.Nine Japanese carriers, backed by a strong escort of battleships, cruisers, and destroyers, sailed towards the Marianas. Most Japanese aircraft were old and many of their pilots were inexperienced and poorly-trained. Admiral Mitscher had 16 fleet carriers waiting with nearly 1,000 planes, most of which were qualitatively superior and had better pilots. The Americans also knew that the Japanese were coming thanks to signals intelligence from the naval station at Pearl Harbor.From June 19 to the evening of the 20th, carrier aircraft from both fleets clashed in big aerial battles. The Japanese attacked first with several waves of over 100 aircraft each. The American fighter defenses had little difficulty shooting down the attackers, leading to the battle being coined the Marianas Turkey Shoot. Before the Americans began launching air strikes on the Kido Butai, the submarines USS Albacore and Cavalla fired torpedoes into the carriers Shokaku and Taih, sinking both. In the evening of the 20th, over 220 American planes attacked the Japanese fleet, sinking the carrier Hiy. Despite significant losses in aircraft, the Americans came off far better, with no ships sunk and some 109 dead. Japan lost three carriers and two oilers, with thousands reported dead. The battle cemented American naval dominance in the central Pacific for the rest of the war and doomed the Saipan garrison.The Fighting in the NorthMarines resting before advancing on Japanese positions on Mt. Tapochau, 1944. Source: First Battalion, 24th MarinesDespite the withdrawal of the Japanese fleet, the garrison on Saipan vowed to fight to the last man. By this point, much of the 47th Mixed Brigade and the 9th Tank Regiment had been destroyed, leaving the Japanese garrison with uncommitted units of the 43rd Division alongside navy and marine personnel. They held a line of fortifications in the middle of the island with the strongest positions being located on Mt. Tapochau. While many Japanese heavy weapons had been destroyed already, General Saitos men still had formidable defenses to fight from.On June 22, the three American divisions commenced an offensive to break Saitos line. The 27th Division faced the toughest challenge because much of the terrain it had to cross was broken. As a result, it fell behind, leading to General Holland Smith replacing its commander, Major General Ralph Smith. By adjusting their tactics, the Americans managed to grind forward through areas known as Death Valley and Purple Heart Ridge. By June 25, the Americans seized most of Mt. Tapochau and five days later, the Americans decisively broke through Saitos defenses.At this point, the Japanese struggled to maintain unit cohesion and their defenses were in disarray. General Smiths main objective was the town of Tanapag and the northernmost airfield near Mt. Marpi. The town of Garapan was taken in tough urban battles and by July 7, the Americans had finally caught the Japanese in a pocket north of Tanapag. General Saito decided to order one final attack.Japans Last Gasp and the Fate of the CiviliansGIs rescue a civilian hiding in a cave in northern Saipan, 1944. Source: The Life Picture CollectionBy this stage in the war, some Japanese commanders urged their subordinates not to launch full-scale Banzai charges, claiming that they were doomed to fail and not capable of inflicting serious losses on the Allies. General Saito was not one of them; he repeatedly ordered counter attacks during the battle. Once it became clear that the battle was over, he decided to launch a massed attack called a Gyokusai with the remaining 4,000 men available. Neither he nor Vice-Admiral Chuichi Nagumo commanding the naval contingent joined the attackers; both committed seppuku before the final assault.On July 6, the Japanese stormed out of their remaining positions to attack the 1st and 2nd Battalions of the 105th Infantry Regiment. Even wounded Japanese servicemen joined the attack without weapons, walking on crutches towards the American lines. Both defending battalions lost close to 900 men due to the surprise of the attack. It was halted under a hail of artillery fire and American reinforcements arriving to assist the 105th. This marked the end of the battle except for clashes with stragglers.The battle engulfed tens of thousands of civilians residing on Saipan. Japanese troops convinced these people that the Americans would commit terrible atrocities against them if they were captured. As a result, over 1,000 civilians took their own lives, often by jumping from cliffs, at the end of the battle. Close to 10,000 others died from artillery or airstrikes during the fighting.The survivors were placed in temporary internment until the end of the battle, when they were allowed to go home to rebuild. The battle proved to be one of the bloodiest in the Pacific so far: nearly every Japanese combatant died while the Americans suffered 16,500 casualties of their own. Nonetheless, the victory was complete, and the Americans could use the airfields to attack Japan. Meanwhile, Prime Minister Tojos government collapsed in Tokyo.