The Battle of Tinian was part of the Pacific campaign of World War II. It was fought between the United States and Japan on the island of Tinian in the Mariana Islands from 24 July until 1 August 1944. The battle saw napalm used for the first time.
At the Cairo Conference in December 1943, the US and British Combined Chiefs of Staff endorsed a two-pronged attack through the Central Pacific and Southwest Pacific Areas. On 12 March 1944, the Commander in Chief, Pacific Ocean Areas, Admiral Chester W. Nimitz, was directed to neutralize Truk and occupy the Mariana Islands. The Mariana Islands were targeted because of their location astride the Japanese line of communications. Tinian lay too close to Saipan to allow it to be bypassed and remain in Japanese hands. Following the conclusion of the Battle of Saipan on 9 July, Major General Harry Schmidt's V Amphibious Corps began preparations to invade nearby Tinian.
The Japanese garrison was commanded by Colonel Kiyochi Ogata, the commander of the 50th Infantry Regiment. This regiment was part of the 5,000 Army troops on the island. There were also about 4,000 Imperial Japanese Navy personnel on Tinian, the main force being the 56th Naval Guard Force, under the command of Captain Goichi Oie. Most of the island was surrounded by coral cliffs, so Ogata concentrated his forces on the southwest of the island, where the best landing beaches were located.
Major General Clifton B. Cates's 4th Marine Division landed on Tinian on 24 July 1944, supported by naval bombardment and the guns of the XXIV Corps Artillery, firing across the strait from Saipan. Instead of landing in the southwest, they landed on the northwest coast, where there were two small beaches that were lightly defended. These beaches were flanked by low coral cliffs that the marines were able to surmount with the aid of ramps mounted on modified amphibious tractors (LVTs). A successful feint in the southwest by Major General Thomas E. Watson's 2nd Marine Division distracted defenders from the actual landing site on the north of the island. The 2nd Marine Division then landed behind the 4th Marine Division. The weather worsened on 28 July, damaging the pontoon causeways and interrupting the unloading of supplies, but on 30 July the 4th Marine Division occupied Tinian Town and the airfield. Japanese remnants conducted a last stand in the caves and ravines of a limestone ridge on the south portion of the island. Although the island was declared secure on 1 August, mopping up patrols continued into 1945.
Tinian became an important base for further US operations in the Pacific. North Field became operational in February 1945 and West Field in March. The Seabees built six 8,500-foot (2,600 m) runways for the Twentieth Air Force's Boeing B-29 Superfortress bombers. Bombers based on Tinian took part in the bombing of Tokyo in March 1945 and the atomic bombings of Hiroshima and Nagasaki in August 1945.
Background
Strategy
After World War I, the United States had developed a series of contingency plans for the event of a war with Japan known as the Orange plans. These envisaged an advance through the Marshall and Caroline Islands to the Philippines, from whence Japan could be blockaded. The Mariana Islands figured only incidentally in the plans, as they lay north of the direct route between Hawaii and the Philippines. During World War II, the islands attracted the attention of naval and air strategists. At the Casablanca Conference in January 1943, the US and British Combined Chiefs of Staff had endorsed an offensive in the Central Pacific along the lines envisaged in the Orange plans. In his formulation of the strategy, the Commander in Chief, United States Fleet, Admiral Ernest J. King, specifically mentioned the Mariana Islands as "the key to the situation because of their location on the Japanese line of communications."
The Joint Chiefs of Staff envisaged the Marianas as a naval base, but another rationale for the capture of the Mariana Islands emerged with the development of the long-range Boeing B-29 Superfortress bomber. From the Mariana Islands, the B-29s could reach all the most significant industrial targets in Japan, and they could be supported by sea. The air staff planners began incorporating the Mariana Islands into their long-range plans in September 1943. The Combined Chiefs endorsed this at the Cairo Conference in December, along with a two-pronged offensive, with the Central Pacific drive in conjunction with one along the north coast of New Guinea. In response, the Commander in Chief, Pacific Ocean Areas (CINCPOA), Admiral Chester W. Nimitz, produced a campaign plan called Operation Granite, which tentatively scheduled the capture of Mariana Islands of Saipan, Tinian and Guam for November 1944 as the culmination of the Central Pacific campaign.
By February 1944, there was consideration of advancing the Operation Granite timetable by bypassing Truk and heading directly for Palau or the Marianas after the capture of the Marshall Islands. On 7 March, Nimitz and his Deputy Chief of Staff, Rear Admiral Forrest P. Sherman met with the Joint Chiefs of Staff in Washington, DC, where they were questioned by the Chief of Staff of the United States Army, General George C. Marshall, and the Chief of Staff to the Commander in Chief, Admiral William D. Leahy. Sherman argued that the neutralization of Truk required the occupation of the Mariana Islands to cut the air route to Truk from Japan. On 12 March, the Joint Chiefs of Staff directed Nimitz to neutralize Truk and occupy the Mariana Islands.
Tinian was considered a target from the outset, Lieutenant General Holland M. Smith's Northern Troops and Landing Force (NTLF) was ordered to "land on, seize, occupy and defend Saipan. Then be prepared to seize Tinian on order." The American forces assaulted Saipan on 15 June. The Battle of Saipan lasted until 9 July, when the island was declared "secured". The cost was high: 14,111 of the 71,034 NTLF personnel were killed, wounded or missing in action. Mopping up operations continued until October, but preparations began immediately for the attack on Tinian.
Plans to capture Tinian were prepared concurrently with those to capture Saipan. Tinian lay only 3.5 miles (5.6 km) from the southern tip of Saipan, and its proximity to Saipan meant that while it remained in Japanese hands, Japanese aircraft could attack Saipan by staging though Tinian. The garrison might raid Saipan, and they could observe ship and aircraft movements on Saipan and communicate them to Tokyo.
Tinian also had value in its own right, as its flat terrain made it highly suitable for the development of air bases. There were already airfields that looked promising for development into B-29 airfields. Ushi Point Airfield (Airfield No. 1) was the main airfield; it had a hard-surfaced runway 4,750 feet (1,450 m) long. Two other airfields were in use and another was under construction: Airfield No. 3, which lay immediately south of no.1; Airfield No. 2, at Gurguan Point; and the unfinished Airfield No. 4 near Tinian Town.
Geography
Along with the other Mariana Islands, Tinian was claimed for Spain by Miguel López de Legazpi in 1565. Guam was seized by the United States in the Spanish-American War, and Spain sold the remaining islands to Germany. They were occupied by Japan during World War I and became part of Japan's South Seas Mandate. Tinian lay just 3+1⁄2 miles (10 km) from the southern tip of Saipan. It covered about 50 square miles (130 km2), measuring 10+1⁄4 miles (20 km) from north to south, and 5 miles (8 km) across at its widest point. The terrain was generally low and flat, making it suitable for airfields. There were two hills in the north: the 390-foot (120 m) Mount Maga and the 564-foot (172 m) Mount Lasso. There was also a rugged 580-foot (180 m) limestone hill mass of cliffs and ravines in the south. About 90 percent of the island (approximately 15,000 acres (6,000 ha)) was covered in sugar cane fields. The square fields gave the island a checker board look from the air. Fields were surrounded by drainage ditches or windbreaks of trees or hedgerows.
Most of the island was encircled by jagged limestone cliffs that ranged from 6 to 100 feet (2 to 30 m) high. There were only a few beaches, which the Americans designated by colors. The best beaches were around Sunharon Bay in the southeast: Blue Beach, 1 mile (1.6 km) south of Tinian Town, was 600 yards (550 m) long; Green Beach One, located between the two piers at Tinian Town, was also 600 yards (550 m) long; Green Beach Two, at the southern end of Tinian Town, was 400 yards (370 m) long; Red Beach One and Two were north of the piers, with a combined width of 825 yards (754 m); and Orange Beach, 1⁄2 mile (0.80 km) north of Red Beach One, was 340 yards (310 m) long.
There were two beaches on the east coast at Asiga Bay: the 355-yard (325 m) Yellow Beach One and the 200-yard (180 m) Yellow Beach Two. These were flanked by cliffs and subject to heavy surf when there was an easterly wind. There were also two small beaches on the northwest coast: the 65-to-75-yard (59 to 69 m) White Beach One and the 200-yard (180 m) White Beach Two. The small size of the White and Yellow beaches made them unattractive: a division normally required a landing beach 1,000 yards (910 m) long.
There was little seasonal variation in temperature, which ranged from an average of 76 °F (24 °C) in January to 80 °F (27 °C) in June, but the average humidity in those months was 78 and 84 percent, respectively. Fair weather prevailed during the dry season from November to March, but the wet season from April to November was characterized by frequent rains and occasional typhoons. Sunharon Bay was little more than an anchorage, and was unusable in rough weather.
According to a 1 January 1944 census, Tinian had a population of 18,000 Japanese civilians, most of whom worked in the sugar cane industry, and 26 ethnic Chamorro people; most of the original population had been forcibly removed to other islands. The main settlements were Tinian Town in the south and two small villages around Ushi Point Airfield in the north. The former was the administrative center of the island, while the latter housed airfield workers. The primary road network consisted of roads approximately 18 feet (5.5 m) wide and surfaced with crushed coral. They were generally straight, following the edges of the cane fields. Approximately 40 miles (64 km) of narrow gauge railways connected the sugar plantations with Tinian Town.
Opposing forces and plans
Japanese
The senior Japanese officer on Tinian was Vice Admiral Kakuji Kakuta, the commander of First Air Fleet. His headquarters was in Manila but he was on Tinian on an inspection tour when US aerial operations in the Marianas Islands began on 11 June and became cut off. He exercised no command authority over the army troops on the island, and the naval troops were not subject to his direct command.
The Imperial Japanese Army force defending the island was the 50th Infantry Regiment, commanded by Colonel Kiyochi Ogata. This was part of the 29th Division, all the rest of which was located on Guam. The regiment was formerly based at Mukden in China, and had moved to Tinian in March 1944. It had three infantry battalions, a mountain artillery battalion with twelve 75mm guns, an anti-tank company with six 37 mm anti-tank guns, and a company of the 18th Infantry Regiment with twelve light tanks. The 1st Battalion, 135th Infantry Regiment, under the command of Captain Bunzo Izumi. Part of the 43rd Division, it had been formed in Nagoya in July 1943. It was normally based on Saipan, but was conducting amphibious landing exercises on Tinian on 11 June and became cut off when Saipan was invaded. It provided a fourth infantry battalion that Ogata incorporated into the island's defense. The Army forces on Tinian totaled about 5,000 men. Most were well-trained combat veterans with prior combat experience in the war in China. They were skilled in camouflage and the use of their weapons. They were well-equipped, in many cases with new weapons, and their morale was high.
The main Imperial Japanese Navy force on Tinian was the 56th Naval Guard Force (Keibitai), under the command of Captain Goichi Oie. He accepted Ogata as the commander on Tinian, but to avoid embarrassment, he did not inform his subordinates that their orders came from an Army officer. His force of 1,400 troops and 600 laborers was equipped with three 6-inch and ten 140 mm coast defence guns, and ten 120 mm and four 76.2 mm general purpose guns, twenty-four 25 mm and six 7 cm antiaircraft guns, and three 12 cm dual-purpose guns. Along with airfield construction crews, flight technicians and staff, there were about 4,000 sailors of various units on Tinian. Most of the naval personnel had some training as infantry. In addition, there were three civilian defence organizations of little military value, the Civilian Militia, the Home Guard Organization, and Youth Organization, and about sixty comfort women, none of whom survived the battle.
After Saipan had fallen on 9 July, the prospects for the garrison of Tinian were grim. Ogata expected that Tinian would be the next target, and on 25 June he issued an operational order that announced: "the enemy on Saipan... can be expected to be planning a landing on Tinian. The area of that landing is estimated to be either Tinian Harbor or Asiga (northeast coast) Harbor." He adhered to the Japanese doctrine of defense against amphibious attacks at the water's edge. Each of the sector commanders was ordered to "be prepared to destroy the enemy at the beach, but be prepared to shift two-thirds of the force elsewhere."
Ogata was aided by the geography of Tinian, which limited the possible landing sites. He positioned the 3rd Battalion, 50th Infantry Regiment and most of the heavy weapons of the 56th Naval Guard Force, around Sunharon Bay beaches. The Northern Sector around Asiga Bay was covered by the 2nd Battalion, 50th Infantry Regiment. He did not expect anything more than a raid on the beaches in the west, so this was assigned to the 3rd Company, 1st Battalion, 50th Infantry Regiment. The rest of the 1st Battalion was dug in around Mount Lasso. The 1st Battalion, 135th Infantry Regiment formed a mobile counterattack force, along with the tanks and a mobile artillery contingent of twelve Type 94 75 mm mountain guns. The reserve was positioned so as to quickly reach either the Sunharon Bay or Asiga bay, depending on where the Americans made their main effort.