Operation Battle of Tinian

The 'Battle of Tinian' was fought between US and Japanese forces for the island of Tinian in the Mariana islands group as part of the US 'Forager' strategic operation (24 July/1 August 1944).

The Japanese garrison of slightly more than 8,000 men was wholly destroyed, and the island then supplemented nearby Saipan and Guam islands as a base for the US 20th Army Air Force for the strategic bombing of Japan.

The island of Tinian, which was earlier known as Bona Vista and had the US codename 'Tearaway', lies 3 miles (4.8 km) due south of the southern tip of Saipan, from which it is separated by a channel characterised by a fast north-eastward current. Guam lies about 85 miles (162 km) to the south-west. Tinian is low by comparison with the other islands of the Marianas group, and is of volcanic origin and covered by rich red soil on a limestone base. The island covers about 39.08 sq miles (101.22 km) and measures 5.5 miles (8.85 km) between the northern Ushi Point and the southern Lalo Point, and 5 miles (8 km) at it widest across the centre. While it is mostly fiat, there are two hills near the north-western end, namely Mt Maga that rises to 390 ft (119 m) above sea level and, just to its south-east, the 564-ft (172-m) Mt Lasso, which the location of the Japanese command post. On the island’s southern end is a 580-ft (177-m) unnamed rugged limestone hill mass with cliffs and ravines. Most of the island comprises an approximately central plateau at a height of about 200 ft (60 m). All level land was cultivated with sugar cane, extending to 90% of the land. The plateau comprised cultivated square or rectangular farm plots bordered by small irrigation ditches or windbreaks of trees and hedgerows, and crisscrossed by a grid of one-lane earth roads. A narrow-gauge railway extended from the own of Tinian with spurs to the south-eastern side, the western coast and the northern, was used to move the cane to the refineries.

Other level ground was occupied by four airfields. These were the 4,700-ft (1435-m) Nos 1 and 3 Airfields near the northern end at Ushi Point, the 5,000-ft (1525-m) No. 2 Airfield on the eastern coast at Gurguan Point, and the incomplete No. 4 Airfield to the north-west of Tinian town. Hilly ground, unsuited for cultivation, was covered with low trees and dense brush. Other than two small villages adjacent to Airfield No. 1, the only town on the island was Tinian town on the south-western coast in Suharon Bay and possessing minimal port facilities. Indenting the upper part of the eastern coast is Asiga Bay.

The island was inhabited by about 15,700 civilians including 2,700 Koreans and just 22 indigenous Chamorros. Most of these persons were employed by the commercial sugar firm. The other Chamorros had long before been forcibly relocated to smaller islands and continued a life based on fishing.

About 5 miles (8 km) to the south of Tinian is the uninhabited Aguijan island, also known as Aguiguan or Goat Island. This measures about 2 by 3 miles (3.2 and 4.8 km) and covers 2.71 sq miles (7.01 km). Its elevation is 584 ft (178 m) and it is surrounded by steep cliffs, which makes access difficult.

The defenders of Tinian were subordinate to the Northern Marianas Army Group headquartered on Saipan. Like the US 'Forager' invasion plan, the Japanese defence plans for Saipan and Tinian were linked. On 7 July, before the fall of Saipan, command of the Japanese garrison of Tinian was shifted to the Southern Marianas Army Group headquartered on Guam. The main Japanese unit on Tinian was the 50th Regiment, detached from Lieutenant General Takeshi Takashina’s 29th Division on Guam. Reinforced by a fourth battalion from Saipan, the regiment was commanded by Colonel Kiyoshi Oganta. The Imperial Japanese army forces on the island totalled 5,050 men, and other elements on the island were the 4,100 men of the Imperial Japanese navy under the command of Captain Oichi Oya. These naval elements included the 56th Guard Force, construction and air service personnel, of whom most were reorganised into infantry units. Vice Admiral Kakuji Kakuta, commanding the 1st Air Fleet, was also located on the island but did not assume or exercise any degree of command.

Most of Tinian’s coast is characterised by jagged limestone cliffs up to 100 ft (30.5 m) in height, and this presented a major problem for the planners of the US assault. The island is also fringed with coral reefs, but these did not pose the same level of difficulty as the cliffs. There are only a few gaps in the cliffs, and these are narrow, which made it feasible for the Japanese to concentrate on the most likely landing sites. The most suitable beaches were on Sunharon Bay in front of and flanking the town of Tinian, but these were heavily defended. Another possible site was the so-called Beach Yellow on the northern part of the eastern shore at Asiga Bay. While considered the second most likely beach by the Japanese commander, it is gap only some 125 yards (115 m) wide in cliffs reaching a height of between 20 and 25 ft (6.1 and 7.6 m).

The other two possible landing sites were Beaches White 1 and White 2 on the north-western coast. The Japanese commander considered Beach White 2 to be a possible secondary landing site and ordered that light defences be established there. Even so, the Japanese did not consider the White beaches to be viable options for the US forces still fighting on neighbouring Saipan. In Japanese estimations, the beaches were simply too small for use by the US forces, which preferred assault beaches suitable for the landing of a full regimental landing team.

Given the extent of the defences on the other beaches, the fact that the assault troops would be tired after a prolonged and difficult fight on Saipan, and the fact that Tinian could be secured at a comparatively leisurely pace, the US planners were persuaded to give serious consideration to the White beaches regardless of their limitations.

Preparatory attacks on Tinian began before the start pf the landings on Saipan. From 11 June, the southern part of the Mariana islands group suffered 3.5 days of air attacks, which destroyed all Japanese aircraft and sank much of the shipping in the area. Naval shellings of Tinian occurred frequently while Saipan was still the location of heavy fighting, and increased from 26 June. Just over one week after the Saipan landings of 15 June, US artillery began shelling Tinian from the southern end of Saipan, and 13 army and marine artillery battalions of Major General John R. Hodge’s XXIV Corps had been concentrated on the southern tip of Saipan to interdict targets on Tinian and then to support the assault.

The beaches of Tinian suitable for amphibious operations were scarce on Tinian, as noted above. The best were located on the south-western shore at the town of Tinian. This is also where the Japanese command expected the US forces to land and therefore accommodated the highest concentration of Japanese troops. The four beaches of Tinian town (designated Beaches Orange, Red, Green and Blue) had a combined assault frontage of 2,100 yards (1920 m), but were separated by sections of low cliff between 200 and 2,000 yards (185 and 1885 m) wide. The selection of the actual landing beaches was a subject of much debate in the highest levels of Admiral Raymond A. Spruance’s 5th Fleet. The US Navy preferred the wider beaches at Tinian town and its Sunharon Bay for the better protection that would be afforded to the protection of mall craft during unloading operations during the expected adverse weather. These beaches were extensively defended and, Beach Yellow on the north-eastern coast was only slightly less well defended. The White beaches were under serious consideration by the marines as there seemed every reason to believe that the Japanese appeared to have developed only limited defences. The navy was also reluctant to begin a fight that would force the marines to drive down the full length of the island, thereby prolonging the battle.

The primary concern over the White beaches was their size. Both were flanked by low cliffs and coral outcroppings, were overlooked by Mt Maga only 2,000 yards (1830 m) to the south, and were under easy observation from the Japanese command post on Mt Lasso 4,000 yards (3660 m) to the south. Airfields Nos 1 and 3, both to the east of the beaches, were ringed with anti-aircraft guns, although most of these had been destroyed. Three 140-mm (5.51-in) guns were dug in at Faibus San Flilo Point less than 3,000 yards (2745 m) to the south-west of Beach White 2. A wooded strongpoint with trenches, dug-outs, and light machine gun and rifle pits lay 500 yards (455 m) to the north-east of Beach White 1.

Beach White 1 was located 1,000 yards (915 m) to the west of the end of Airfield No. 1. It was only 60 yards (55 m) wide, hardly the usual 1,200 yards (1100 m) deemed desirable for the landing of a full regiment with two battalions abreast. It offered an approach 200 yards (185 m) wide across the coral reef, which is on the order of 50 yards (45 m) wide. The beach was as shallow as it was narrow, a matter of just a few yards at low tide. Coral outcroppings and ledges littered the beach, which was backed by a belt of brush between 20 and 30 yards (18.3 and 27.4 m) wide. An equally wide belt of low trees, free of underbrush, backed the brush line, and behind these were the sugar cane fields crisscrossed by dirt roads.

Beach White 2 was 1,000 yards (915 m) to the south-west of Beach White 1. It was 160 yards (145 m) wide, but only the central 65 yards (59.5 m) were free of coral outcroppings and ledges. Those on the rest of the beach averaged 3.5 ft (1.-7 m) in height. The beach offered an approach 400 yards (365 m) wide. There was a sloping seawall, man-made of coral rock to a height of 2 ft (0.61 m), behind the beach, but vehicles could mount it with ease. A narrow belt of brush and scattered trees backed the beach and then the usual cane fields and grid of roads.

Each of these beaches was flanked by coral cliffs between 6 and 10 ft (1.8 and 2.1 m) in height, and while low, these cliffs were sharp and jagged, and having been undercut by wave action would be difficult for the marines to scale.

While senior commanders argued about the suitability of the White beaches, the marines and the navy conducted a reconnaissance of the White beaches and Beach Yellow in order to reduce their reservations. The beaches were far smaller than any previously used for the landing of a regiment, much less a reinforced division to be followed by a second. If one of the White beaches was unsuitable, one might be used along with Beach Yellow. This plan offered a the possibility of two-prong attack, but the problem lay in the fact that the two beaches lay on opposite sides of the island and were separated by 6,000 yards (5485 m) of defended terrain. Reconnaissance of the White beaches was encouraging and the navy finally agreed to the plan.

Habitually, supplies were landed directly onto beaches from amphibian tractors, DUKW amphibious trucks and ramped landing craft. Supplies were stockpiled in dedicated dumps, then moved inland and distributed to front-line units. The very small size of the White beaches precluded any such possibility on Tinian, and supplies would have to be moved inland by tractors and DUKWs to dumps well clear of the beaches. The beaches would be highly congested with landing and departing amphibious vehicles, and this meant that the two leading assault regiments, one on each beach, had two essential missions besides closing with and destroying the Japanese: firstly, they had to establish contact with each other over the 1,000-yard (915-m) interval between the beaches and thereby create a single beach-head, and secondly, they would have to drive inland as far and as fast as resistance permitted to provide the depth necessary for the siting of supply dumps, artillery positions, command posts, aid stations and reserve units.

The assault-loaded transports and landing craft carrying the bearing Major General Harry Schmidt’s 4th Marine Division and Major General Thomas C. Watson’s 2nd Marine Division departed Saipan on the night of 23 July and within hours were positioned off of the White beaches. Major General Ralph C. Smith;s 27th Division remained on Saipan as the area reserve and continue mopping up, and in fact did not land on Tinian. On the morning of 24 July, the 2nd Marine Division conducted a feint off Tinian town to reinforce the Japanese belief that this was to be the location of the main assault. Air attacks swept the island between lulls in the gunfire bombardment by the naval force and the XXIV Corps' artillery on southern Saipan. Frogmen of Underwater Demolition Teams 5, 6 and 7 attempting to destroy coral boulders and any anti-boat mines on White 2 were foiled by a rainstorm. One battleship, two cruisers and four destroyers supporting the assault fired directly into the beaches in hopes of destroying any mines. A force of 30 gunboats fired guns and 4.5-in (101.7-mm) rockets into the beach areas. This was followed by on-call aircraft attacks. Air observers reported possible mines left on the beaches. Artillery on Saipan laid smoke on Mt Lasso to prevent Japanese direct observation of the beaches. The marine amphibian tractors headed toward the shore regardless of possible mines.

On Beach White 1, Company E, 2/24th Marines landed at 07.47, and the rest of the battalion followed in a column of companies as did the 1/24th Marines. Eliminating resistance from caves and crevasses, the 24th Marines had secured a line 1,400 yards (1280 m) inland by 16.00. The 25th Marines assaulting Beach White 2 took advantage of the slightly wider extent of this beach and landed two battalions abreast. The Japanese resistance stiffened as the 25th Marines pushed inland, and this prevented them from reaching Mt Maga. However, the two marine regiments quickly established contact between the two beaches. Despite the small size of the beaches, mines, resistance and rain, 15,600 marines had landed by the end of the first day. Lieutenant General Holland M. Smith, commander of the V Amphibious Corps, in a rare favourable statement called the Tinian assault 'the perfect amphibious operation'. This is often attributed to the operation’s many departures from accepted amphibious doctrine and flexibility in planning, both of them factors critical for any successful military operation.

The 2nd Marine Division landed on the following day and the drive to the south resumed, but this slowed as the Japanese were pushed onto the island’s narrow and rugged southern end. Organised resistance had dwindled by 1 August and the island was declared secure at 18.55. The marines had lost 330 men dead and more than 1,570 wounded. More than 5,000 Japanese dead were counted and thousands more were buried in caves and bunkers. Prisoners numbered 250 by one count and 500 by another, possibly owing to confusion with civilian internees. Another 4,000 or so civilians had been killed in the pre-invasion bombardment and during the fighting ashore.

The Naval Base, Tinian was established in Tinian town on Sunharon Bay as a cargo ship port to supply the bomber units being established on the island, which was being literally leveled as new airfields were constructed; more than 8 million cu yards (6116440 m) of coral fill were used to construct the six main runways, taxiways and hardstandings. Immense support facilities were built. The first of the airfields was the 6,000-ft (1830-m) West Field built for the navy in November 1944, using the old No. 2 Airfield. Two 8,500-ft (2590-m) runways were added to the West Field, which was taken over by the US Army Air Forces as a Boeing B-29 Superfortress four-engined strategic bomber base. It was ready in March 1945, though still used by the navy as Naval Air Base, Tinian. The North Field was built over the old Nos 1 and 3 Airfields. It became operational in February 1945 and by May had four 8,500-ft (2590-m) B-29 runways. Mine Assembly Plant No. 4 served as an aerial mine depot for the B-29 forces tasked with the mining of Japanese ports, and assembled more mines than all other US mine depots together.

It was from Tinian that B-29 bombers took off to drop atomic bombs on Hiroshima and Nagasaki on 6 and 9 August 1945.

The air bases were closed after the war and much of the debris was bulldozed to the island’s edges. The centre of the island has overgrown with brush and high grasses. The naval base and naval air base were closed on 1 June 1947.