The bombardment of Iwo Jima

On 8 December 1944 American aircraft and warships carried out a coordinated strike on Iwo Jima, a small volcanic island in the Volcano (Kazan) Islands, lying roughly halfway between the Marianas and Tokyo. In the morning P-38 fighters arrived over the island, followed by B-29 and B-24 bombers, and in the afternoon heavy cruisers joined in the bombardment. From that day the four-engined Consolidated B-24 Liberators of the Seventh Air Force, based on Saipan and Guam, attacked Iwo Jima every day – right up to the American landing on 19 February 1945. According to the official history of the operation published by the Marine Corps, the raids went on without a break for 74 days.

It is often said that 8 December saw the start of the bombardment preparing Iwo Jima for invasion. The date is correct but needs qualifying. The island had been under attack since June 1944 – first by carrier aircraft and from August also by bombers from the Marianas. What began on 8 December was a new phase: daily, systematic bombing which, according to American studies, was the longest air preparation before any landing in the Pacific. As it turned out, its effect on the Japanese defences was far smaller than expected.

An island halfway

Iwo Jima (“Sulphur Island”) covers about 21 square kilometres. Its southern tip is closed off by the extinct volcano Suribachi, rising to 169 metres; the rest is a plateau covered in black volcanic ash. It lies some 1,200 kilometres south of Tokyo and almost the same distance north of Saipan. The Japanese had built two airfields there, and a third was under construction. Before the war the island had a little over a thousand civilian inhabitants – in July 1944 all of them were forcibly evacuated to Honshu.

After the capture of Saipan and the other islands of the Marianas in the summer of 1944, Iwo Jima’s importance grew sharply for both sides. For the Japanese it was an outpost of the home islands: its radar station warned Tokyo of approaching bombers, fighters from its airfields could intercept them, and aircraft from Japan landed there to refuel before attacking the Marianas. For the Americans the island was an obstacle on the bombers’ route, but it could also become a base: an airfield for escort fighters, which lacked the range to accompany the B-29s from the Marianas to Japan, and an emergency airfield for bombers damaged over the target.

On 3 October 1944 the Joint Chiefs of Staff, settling the dispute over the road to Japan, instructed Admiral Chester Nimitz to take Iwo Jima and then Okinawa. The operation was named Detachment. It was originally to begin at the end of January 1945, but the prolonged fighting in the Philippines, including the Battle of Leyte, meant that the date was put back to 19 February.

Earlier attacks and the Japanese raids on Saipan

The first American strikes fell on Iwo Jima as early as 15 and 16 June 1944, when two carrier groups detached from the fleet covering the landing on Saipan attacked the airfields on the island and on neighbouring Chichi-jima and Haha-jima to prevent the Japanese from moving aircraft to the Marianas. The carriers returned several more times during the summer. From August the Seventh Air Force’s B-24s from the Marianas flew regularly against the island, but their effort was dispersed. According to the official history of the US Army Air Forces, two heavy bomber groups had at the same time to keep watch on Truk, the Marshall Islands and other bases, and at the navy’s request a considerable part of the sorties was directed against shipping in the harbours of Chichi-jima and Haha-jima, with indifferent results.

The situation was changed by the B-29s in the Marianas. As bombers being readied for attacks on Japan began to accumulate on the airfields of Saipan, Japanese aircraft – landing on Iwo Jima on the way – began to attack them. The first raids, at the beginning of November, did little damage. On 27 November, the day of the second mission against Tokyo (the first, the B-29 raid on Tokyo, had taken place three days earlier), two bombers caught B-29s on the ground while bombs were being loaded, destroying one and damaging eleven, and at midday a dozen or so fighters slipped in low under the radar cover and destroyed three more. On 7 December, attacking simultaneously from high and low altitude, the Japanese destroyed three B-29s and damaged twenty-three.

These raids cost the Japanese many aircraft – according to the American official history, more than 80 machines came over Saipan and Tinian up to 2 January 1945, of which some 37 were lost. Yet the exchange was worth it for them: they destroyed 11 B-29s and seriously damaged another 8 and lightly damaged 35, while 45 Americans were killed and more than 200 wounded. The B-29 was the most expensive aircraft of the war, and XXI Bomber Command was only just beginning its campaign.

The strike of 8 December

On 24 November Nimitz ordered that Iwo Jima become the main target of the land-based aircraft in the Marianas, putting an end to the unsuccessful attacks on shipping. It was soon decided to carry out a single powerful strike from the air and the sea, which was to put the Japanese airfields out of action. Lieutenant General Millard F. Harmon, commander of the Army Air Forces in the Pacific Ocean Areas, flew to Saipan on 5 December with a plan to use all the available P-38 fighters, B-24 and B-29 bombers and Cruiser Division 5. The attack was set for noon on 7 December, but bad weather forced a postponement of twenty-four hours.

On 8 December, although the sky was still overcast, the plan was carried out. At 9.45 a.m. 28 Lockheed P-38 Lightning fighters arrived over the island, at 11 a.m. the B-29s, and at noon the B-24s. Sixty-two Superfortresses dropped some 620 tons of bombs, 102 Liberators only 194 tons. The air force official history notes that this difference showed clearly the superiority of the new bomber over the older one at a range of more than a thousand kilometres. Harmon had hurriedly agreed the details on Saipan with, among others, the commander of XXI Bomber Command, Brigadier General Haywood S. Hansell, while the chief of the Army Air Forces, General Henry H. Arnold, worried by the losses on Saipan’s airfields, enthusiastically agreed to the one-off diversion of the B-29s from their strategic task.

At 1.47 p.m. the heavy cruisers of Rear Admiral Allan E. Smith’s Cruiser Division 5 – Pensacola, Chester and Salt Lake City – opened fire. Since November the division had been shelling the Volcano and Bonin (Ogasawara) Islands from time to time. The bombardment lasted 70 minutes. According to her ship’s history, USS Pensacola alone fired some 500 8-inch (203 mm) shells.

The results proved modest. The clouds forced the bombers to drop by radar, and aerial photographs, also hampered by the weather, showed – as the air force official history admits – results “far less decisive than had been expected”. The Japanese raids on Saipan nevertheless ceased for more than two weeks. They were resumed on Christmas night, when some 25 aircraft destroyed one B-29 and damaged three more beyond repair. The last Japanese bomb fell on Saipan on 2 January 1945.

Seventy-four days of raids

After 8 December the B-29s returned to their attacks on Japan, and the task of “neutralising” Iwo Jima was taken over by the B-24s of the 11th Bombardment Group from Guam and the 30th Group from Saipan. Two squadrons day after day dropped mainly 500-pound (225 kg) bombs on the island. According to the Army Air Forces official history, in December the two groups flew 79 missions against Iwo Jima, and between November and January 1,836 combat sorties. The daylight raids were followed by night sorties by single aircraft intended to hinder Japanese repairs. At night North American B-25 Mitchell bombers of the Marine squadron VMB-612, armed with rockets and radar, also hunted Japanese supply ships around the Volcano and Bonin Islands. Smith’s cruisers returned to Iwo Jima on 24 and 27 December and on 5 and 24 January 1945, each time together with the bombers. From the end of January the Liberators were flying 30–34 sorties a day.

This campaign, however, had clear limits. According to the air force official history, all the airfields on the island were never put out of action at the same time, and none was unusable for a full twenty-four hours – the Japanese filled in the craters every day. The Christmas attack on Saipan was carried out the day after one of the heaviest combined air and sea strikes. The same sources concede, at the same time, that the constant bombing made it difficult for the Japanese to use the airfields as staging points and contributed to the end of the raids on the Marianas.

Kuribayashi’s defence

The bombs achieved even less against the island’s defenders. In June 1944 command of the garrison was taken over by Lieutenant General Tadamichi Kuribayashi, commander of the 109th Division, a cavalryman who at the end of the 1920s had spent two years in the United States (studying, among other places, at Harvard University) and then served as military attaché in Canada. He had no illusions about American industrial might. He concluded that the island could not be held, but that it was possible to inflict such losses on the attacker as to delay the assault on Japan and make the Americans think twice about invading the home islands.

Kuribayashi broke with the previous practice of defending the beaches and launching suicidal counter-attacks, which on Saipan had led to the rapid destruction of the garrison. Like the defenders of Peleliu in September 1944 (in the Battle of Peleliu), he prepared a defence in depth inland, based on mutually supporting bunkers, artillery positions and caves. Some 21,000 army and navy troops were assembled on the island. Tunnels were dug – by February 1945 some 18 kilometres of the planned 27 had been completed – linking fighting positions, stores and underground command posts, some of them more than 20 metres below ground. The tanks of the 26th Regiment of Lieutenant Colonel Takeichi Nishi, the 1932 Olympic equestrian champion, were dug in as static firing positions. The Suribachi area was prepared for independent defence, because the tunnel linking it to the rest of the island had not been completed.

Instead of destroying these fortifications, the bombing accelerated their expansion underground. The official Marine Corps monograph notes that according to aerial photographs from early 1945 the number of field fortifications, bunkers and covered artillery positions was growing despite the raids. Some American planners, meanwhile, unaware of the scale of the tunnel system, believed that the continuous bombing had wiped out most of the garrison.

Place in the war

The bombardment that began on 8 December continued without interruption until the invasion. The Marines asked for ten days of heavy naval gunfire immediately before the landing, but the navy agreed to only three – from 16 to 18 February 1945 – citing, among other things, the need to replenish ammunition and the simultaneous carrier strikes on Japan. On 19 February the 4th and 5th Marine Divisions landed on the beaches in the south-east of the island, later followed by the 3rd Division. The Battle of Iwo Jima had begun, one of the bloodiest in the history of the US Marine Corps. On 23 February Marines raised the flag on the summit of Suribachi, but the fighting went on until 26 March. Some 6,800 Americans were killed, and total American casualties – more than 26,000 killed and wounded – exceeded Japanese losses, the only time this happened in the great Pacific landings. Of the roughly 21,000 defenders only 216 were taken prisoner. Kuribayashi was killed at the end of March.

The island then fulfilled the purpose for which it had been taken: according to the air force official history, 2,251 B-29 landings were recorded there by the end of the war, and North American P-51 Mustang fighters escorting the bombers over Japan took off from its airfields. Historians nevertheless debate whether these benefits were worth the losses, since many of the damaged aircraft would have been able to make it back to the Marianas. The lessons of Iwo Jima – above all how little air power and naval gunfire could achieve against defences hidden in rock – influenced the preparations for the Battle of Okinawa, which was preceded by the heaviest bombardment of any Pacific island up to that time, and the plans for the invasion of the Japanese home islands.