The Capture and Use of the Marianas

With the capture of the Marianas, U.S. forces gained a defensible, easily supplied set of airfields capable of sustaining hundreds of Superfortresses at one time. Of the major Japanese home islands, only Hokkaido lay beyond Superfortress range from Saipan. 

Admiral Nimitz coordinated the sea, land, and air forces that secured the southern Marianas during the summer of 1944. Saipan fell at great cost in a brutal campaign during June and July. Nimitz captured Tinian in July and Guam in August. The U.S. conquest of the southern Marianas shook Japanese political and military rulers, who correctly reasoned that the Americans would bomb Japan from the captured islands. In July 1944, a retired general, Kuniaki Koiso, replaced Gen. Hideki Tojo as premier, primarily because of the successful American invasion. Although more moderate than Tojo, Koiso refused to consider surrender. He realized Japan’s vulnerability to air attack from the Marianas, but was far from concluding that the war was lost. 

As the Japanese adjusted to the loss of Saipan, Tinian, and Guam, the United States prepared for B–29 operations based in the Marianas. Nimitz coordinated his activities with those of the AAF through Lt. Gen. Millard Harmon, who became commander of the AAF, Pacific Ocean Areas, on August 1, 1944. The former head of army forces in the South Pacific wore two hats: exercising operational control of all land-based planes in the Pacific theater, Harmon reported directly to Nimitz; and, as deputy commander of the Twentieth Air Force, he reported to Arnold in Washington. 

Arnold reserved operational control of the Superfortresses in the Marianas for the XXI Bomber Command under Hansell, former chief of staff of the Twentieth Air Force. On October 12, Hansell landed at Isley Field on Saipan in the first B–29 to reach the Marianas, and soon the 73d Bombardment Wing arrived with its complement of Superfortresses. Before the month ended, Hansell launched the first shakedown flight: fourteen B–29s struck the submarine pens on Dublon Island, several hundred miles south-eastward in the Caroline Islands. 

Hansell’s strategic targets were handpicked by the Joint Chiefs of Staff. First priority went to aircraft factories because that industry, like the steel facilities targeted during Matterhorn, was considered particularly vulnerable, and the bombing would affect the enemy’s performance against MacArthur’s offensive in the Philippines. Other targets included port facilities in the major cities of the Japanese empire. 

Hansell prepared carefully for his first strategic missions. On November 1, the Tokyo Rose flew a photographic mission over the Japanese capital, marking the first appearance of an American aircraft in the skies over Tokyo since the Doolittle raid more than two-and-a-half years earlier. Later that month, reconnaissance versions of the B–29 flew seventeen more sorties. On November 24, more than six weeks after he had arrived on Saipan, Hansell finally unleashed San Antonio I, the first Superfortress attack on Japan from the Marianas. One hundred eleven B–29s, 90 percent of the Superfortresses on Saipan, set off for Tokyo, led by Brig. Gen. Emmett O’Donnell, Jr., 73d Bombardment Wing commander, in Dauntless Dotty.

 The mission had only symbolic success. Many of the bombers ran short of fuel and turned back; others failed to bomb because of mechanical difficulties. Eight Superfortresses were damaged by the enemy, and one was lost in combat. At high altitude, the remaining bombers encountered strong jet stream tailwinds that pushed them over the targets at a speed of 445 miles per hour. Only 35 of the 111 B–29s managed to bomb the primary target, the Musashino aircraft factory. A mere 48 bombs hit the factory area, damaging 1.0 percent of the building and 2.4 percent of its machinery. 

Three days later, Hansell launched San Antonio II. Eighty-one Superfortresses bombed aircraft factories and docks in Tokyo, using radar because of cloud cover, but they did little damage. However, the news was not all bad: the raid showed that airmen could sustain a bombing campaign from the Marianas and that most Japanese interceptors and antiaircraft artillery were still ineffective. 

Not until January 1945 did Hansell demonstrate the potential of precision bombing tactics with B–29s against Japan. On January 19, his Superfortresses practically shut down the Akashi works of the Kawasaki Aircraft Industries Company near Kobe, which in 1944 had supplied 17 percent of Japan’s airframes and 12 percent of its airplane engines. The raid cut the plant’s production by 90 percent. Unfortunately for Hansell, the destructiveness of the January 19 raid was not confirmed until much later.