The Battle of Saipan took place in June-July 1944. US forces engaged in a titanic three-week struggle with Japanese defenders to finally take the island, part of the Mariana Islands, during the Pacific War of WWII (1939 to 45). The battle for Saipan inflicted total casualties of over 45,000. Control of the island and others in the archipelago allowed the US to operate airfields with B-29 bombers that were now close enough to bomb any city in Japan.

Seeking to push back the Japanese Empire in the Pacific and gain revenge for the Japanese attack on Pearl Harbor in December 1941, US naval forces earned a sort of draw in the Battle of the Coral Sea in May 1942. A clear-cut victory was then achieved at the Battle of Midway the next month, the US fleet sinking four Japanese carriers for the loss of one of their own. The Imperial Japanese Navy was now, for the first time, obliged to go on the defensive. Another important US victory was gained in the Guadalcanal Campaign in the Solomon Islands, fought between August 1942 and February 1943.

The industrial might of the US permitted the arrival of new weapons, aircraft, carriers, and amphibious vehicles to this theatre of the war. Japan's defeat in the Gilbert and Marshall Islands Campaign (November 1943 to February 1944) allowed the US to secure its vital supply lines back to Australia and 'island-hop' its way deeper into the central Pacific region. Each new island group taken from the Japanese allowed the US forces to build up a new base from which a new strike could be launched further north.

The main Japanese naval and air base in the Pacific was at Truk Atoll (modern name: Chuuk Lagoon, part of the Caroline group). US forces launched a powerful strike against Truk on 17 February 1944 as part of the Gilbert and Marshall Islands Campaign. Operation Hailstone, as it was called, destroyed the base, but the main ships of Japan's Combined Fleet had already left the lagoon. The Japanese military government was aware that Truk was no longer a defensible haven for its carriers and battleships and had withdrawn them to safer waters further north.

By mid-1944, the rest of the Caroline Islands had been secured or simply bypassed in the war. The next US objective was the Mariana Islands, specifically Saipan and Guam. Although Guam was the southernmost island in the archipelago, it was Saipan that would be struck first.

The Mariana Islands had been controlled by Japan ever since it gained them after the First World War (1914 to 18) as a mandated territory of the League of Nations; they were previously part of the German Empire. The islands were vital to Japan's Pacific communications network, and they had been steadily reinforced in recent months, although US submarines had caused havoc with this operation and sunk many ships destined for the archipelago. Nevertheless, by the summer of 1944, the Marianas were packed with around 60,000 Japanese troops.

The islands were quite different in terms of terrain from those conquered in earlier US amphibious operations. Unlike the low-lying coral atolls of the Gilbert and Marshall Islands, the Mariana Islands were rugged volcanic islands with mountainous and densely vegetated interiors. Weeding out well-set defenders would be a much more difficult task here.

Saipan was the US's first target, but it was not an easy island to storm since it was the most strongly defended in the Mariana group. It is 14 miles (22 km) long and 6.5 miles (10.4 km) wide with high ground from which the Japanese defenders could bombard the beaches. It also had its own airstrip at the southern end of the island, Aslito airfield, and a secondary airfield at the northern end. The approach to the beaches was protected by a continuous reef, and so US underwater demolition experts first had to blast channels through the coral to allow the amphibious landing vehicles to get through.

A tough task lay ahead, but the US troops were no doubt buoyed by the news that D-Day had begun in Europe, that is, the Normandy Landings of 6 June. The two remaining Axis powers of Germany and Japan were in retreat. US commanders were optimistic that Saipan would be captured in three days. In reality, the battle raged for three weeks.

The attack began on 11 June 1944 with a naval and air bombardment, but this was insufficient to seriously dent the defensive capabilities of the 32,000-strong Japanese force defending Saipan. 8,000 men taken from two US Marine divisions were transported in 600 LVTs (Landing Vehicles, Tracked) to land on the western beaches of Saipan on 15 June. They were led by Lieutenant-General Holland 'Howlin' Mad' Smith (1882 to 1967), who acquired his nickname for his heroic exploits in WWI when he won the Croix de Guerre medal. More useful to this campaign was the fact that Smith had been one of the pioneers of amphibious warfare and the architect of just what it meant to be a US Marine through the late 1930s. Smith was certainly a character on the beach, with his squat figure, spectacles, and ever-present cigar.

Over the next two days, more Marines poured in – the total landed on Saipan reaching around 20,000 – but casualties were high, with around 4,000 killed and wounded. The Japanese commander on the ground, Lieutenant-General Saito Yoshitsugu (1890 to 1944), had, in fact, managed to reorganise his forces well, considering the landing had not come at the beach he had anticipated it would. He also hoped that by keeping the US force pegged back onto the beach, a Japanese naval bombardment could make short work of them. This was not to be since the Japanese fleet was otherwise engaged further west in the Philippine Sea. The arrival of a unit of US tanks helped secure the beachhead and repel Japanese counterattacks.

Another US division was landed on Saipan, this time the Army's 27th Infantry Division. The US forces captured Saipan's southern airstrip on 18 June and then gradually moved northwards. The Japanese, meanwhile, retreated to a successive series of defensive lines from where they could make counterattacks using their own tanks. 'Howlin' Mad' Smith lived up to his name again when he dismissed his namesake Major-General Ralph C. Smith, who commanded the 27th Infantry Division, for being too slow in the advance and so exposing the two Marine divisions to a flanking counterattack. The US Army was outraged that a US Marine general should dictate who commanded an Army division, but this was all part of a steep learning curve for the US armed forces. The better commanders were fast realising that victory against a tenacious enemy would only come from a fully coordinated effort using the combined services of the navy, naval air force, marines, army infantry, army air force, and military intelligence.

The Japanese defenders, faced with more and more Marines landing, were eventually obliged to retreat to the centre of the island. Here the terrain around Mount Tapotchau (which is around 1,500 feet or 457 metres high) and the ingrained Japanese belief that surrender was dishonourable combined to make taking control of the whole island a bloody task for the Marines. One wooded area became known as 'Purple Heart Ridge' (after the US medal for wounded or killed service personnel) because so many casualties were suffered there. Indeed, the first attempt to take this ridge failed, and a new commander was selected to try for a second time. The ground troops benefitted from US naval fire which struck at concentrations of the defenders spread out in the deep valleys of the interior. Nevertheless, every cave and potential hiding place had to be cleared out using a combination of flamethrowers, grenades, Bangalore torpedoes, and TNT explosives.

When the Japanese realised that they could no longer defend their positions, a banzai charge – the largest of the Pacific War – was launched on the night of 6 July. So called because the soldiers cried out Tenno heika banzai ('Long Live the Emperor'), this charge was a suicidal mission to cause as many casualties amongst the enemy before dying in what was considered an honourable death. Even after this action, several isolated pockets of Japanese soldiers fought on. The battle only officially ended on 9 July when the few remaining Japanese soldiers and a handful of sympathetic civilians chose to jump off the cliff at Marpi Point rather than surrender. Saito Yoshitsugu also committed suicide.

In total, the US forces suffered around 16,500 casualties while the Japanese figure stood at around 29,000 (Smurthwaite). The US had won another leap forward in the Pacific War's race to Tokyo. Fleet Admiral Osami Nagano, naval adviser to the emperor, exclaimed when he heard news of Saipan's fall: “Hell is on us!” (Leckie, 210)

Another crushing Japanese defeat came at the contemporary Battle of the Philippine Sea (19 to 20 June) where, in the war's largest carrier battle, around 400 Japanese aircraft, 17 submarines, and three aircraft carriers were lost. The Japanese Imperial Navy had hoped to defeat the US task force which had been assigned to protect the US Marines landings on Saipan (and subsequently on Guam), but, not for the first time, an overly complex plan went awry very early. The much larger US fleet and accompanying aircraft were not to be separated in diversionary attacks. The one-sided air battle against the technologically inferior Japanese planes and their insufficiently trained pilots was called by the US pilots and anti-aircraft gunners 'The Great Marianas Turkey Shoot', such was the ease of victory. The Battle of the Philippine Sea effectively destroyed the Imperial Japanese Navy's capability to conduct an offensive war.

At the same time as the Battle of Saipan, the US began its strategic bombing campaign against Japan itself using bases in China. The possession of Saipan now meant that US long-range bombers in the form of the Boeing B-29 Superfortress could use the island as a base and strike any Japanese city. This was preferable to the bases in China because the Marianas were much easier to resupply.

After the loss of Saipan, the Japanese prime minister, General Hideki Tojo (1884 to 1948), no longer supported by the Japanese emperor, was ousted from power in Tokyo on 18 July. Tojo was replaced by Kuniaki Koiso (1880 to 1950), but the war went on.

The next major confrontation in the Pacific War would be the battles of Guam and Tinian, also in the Mariana Islands, in July 1944. Victory here would be followed by those achieved in the Battle of Iwo Jima and Battle of Okinawa in the spring of 1945. Japanese forces fought with tremendous tenacity and, even in defeat, inflicted heavy casualties on the US forces. Finally, the terrible destruction of Hiroshima and Nagasaki using nuclear bombs brought Japan's surrender in August 1945.