Tallboy and Grand Slam

Grand Slam bomb exploding near Arnsberg viaduct 1945.

Lancasters distinguished themselves in the evening skies over Europe by delivering 608,612 tons of bombs in 156,000 sorties. However, they are best remembered for two very special attacks. The first, launched against the Mohne and Eder dams on May 17, 1943, utilized the famous Barnes Wallis "skipping bomb" that demolished its targets. The second fell upon the German battleship Tirpitz in Norway. On November 12, 1944, 31 Lancasters armed with 12,000-pound "Tallboy" bombs finally sank the dreaded raider in a fjord. By war's end, Lancasters had been modified to carry the 22,000- pound "Grand Slam" bomb.

Barnes Wallis scaled down his proposals for his gravity-assisted penetrating bomb, and in 1944 designed instead the 12,0001b (5,400kg) Tallboy bomb, which could be carried by the current bombers. Later in the war, the Avro Lancaster improved to such an extent that it could just support a 10-ton payload and so, as we shall see, the 22,0001b (10,000kg) Grand Slam bomb was finally put into production. It was a secret weapon of unprecedented power. As in the case of the Tallboy bomb, the Grand Slam was spin-stabilized by its fins and was built with a thick, heavy steel case to allow it to penetrate deep layers of the ground unscathed. Dropped from high altitude, it would impact at nearly the speed of sound. During manufacture, hot liquid Torpex explosive was poured in to fill the casing and this took a month to cool down and solidify. Torpex (named because it had been developed as a TORpedo EXplosive) had more than 150 per cent the force of TNT The finished bomb was so valuable that aircraft that could not drop their weapon in an abortive mission were ordered to return to base and land with the bomb intact, instead of jettisoning it over the open sea. 

Barnes Wallis had planned to create a 10-ton weapon in 1941, but it was not until June 1944 that the bomb was ready for use. It was first dropped on the Saumur rail tunnel from Lancaster bombers of 617 Squadron. No aircraft were lost on the raid, and one of the bombs bored 60ft (18m) through the rock into the tunnel, blocking it completely. These massive 'earthquake' bombs were also used on the great concrete structures that the Germans were building to protect their rocket storage bunkers and submarine pens, and caused considerable damage. The Valentin submarine pens at Bremen, Germany, were made with reinforced concrete roofs some 23ft (7m) thick yet they were penetrated by two Grand Slam bombs in March 1945.

Japanese Home Islands Bombing

YB-29 Superfortresses in flight.

On May 14, 1945 472 B-29s attacked the area in and around the Mitsubishi engine factory at Nagoya. Two nights later, another visit to Nagoya devastated another four square miles of that city. On May 23 and May 25, Tokyo was hit again. Although these two Tokyo raids had cost 43 B-29s, over 50 percent of the city had now been destroyed.

Alarmed at the increasing B-29 losses, a change of tactics was ordered. In an attempt to confuse the enemy defenses and to lure Japanese fighters into an air battle in which many of them would be destroyed, high-altitude daylight attacks were temporarily resumed. On May 29, 454 B-29s appeared over Yokohama, but this time they were escorted by P-51 Mustangs from Iwo Jima. In the resulting dogfight, 26 Japanese fighters were destroyed against the loss of four B-29s and three P-51s. 

Thereafter, the Japanese hoarded their surviving fighters for a last-ditch effort against the inevitable invasion force, and the air defense of cities became a lesser priority. By June of 1945, Japanese interceptors were seen much less frequently and the B-29s had free reign over all Japanese airspace.

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Despite widespread awareness about the vulnerability of the Japanese home islands to air attack—reinforced by the results of the Doolittle Raid on Tokyo on 18 April 1942—U.S. plans for an air war against Japan remained vague until well into 1943 because of American limitations in resources and technology.

The development of the Boeing B-29 Superfortress changed this situation. Eventually, more than 1,000 of the long-range aircraft were deployed in the Twentieth Air Force under the direct control of the Army Air Forces commander, General Henry “Hap” Arnold, subdivided into the XX and XXI Bomber Commands. Under pressure to get results from his expensive very-heavy bomber program, he fielded the new aircraft even before testing had been completed.

In June 1944, B-29s from Major General Kenneth Wolfe’s XX Bomber Command began bombing Japan from China as part of Operation MATTERHORN. The campaign was plagued by logistical problems that got worse when Japanese troops overran advanced Allied airfields in China. Arnold replaced Wolfe with the USAAF’s premier problem-solver, Major General Curtis LeMay. However, even he could not make MATTERHORN a success. Arnold’s greatest hopes for an airpower victory over Japan rested with Brigadier General Haywood “Possum” Hansell’s XXI Bomber Command, which began operations from the Mariana Islands in November 1944. Hansell was one of the architects of the precision-bombing doctrine, but his operations also had little success.

Poor facilities, faulty training, engine failures, cloud cover, and jet streams at bombing altitudes made precision methods impossible. Hansell seemed unwilling to change his tactics, however, and Arnold feared that he would lose control of the heavy bombers to Allied Pacific theater commanders without better results, so he consolidated both bomber commands in the Marianas under LeMay and relieved Hansell.

LeMay instituted new training and maintenance procedures but still failed to achieve useful results with daylight high-altitude precision attacks. He decided to resort to low-level incendiary raids at night. Although area-firebombing went against dominant Air Forces doctrine, flying at low altitude reduced engine strain, required less fuel, improved bombing concentration, avoided high winds, and took advantage of weaknesses in Japanese defenses. LeMay’s systems analysts predicted that he could set large enough fires to leap firebreaks around important industrial objectives. His first application of the new tactics, Operation MEETINGHOUSE, against Tokyo on the night of 9 March 1945, produced spectacular destruction and was the deadliest air raid of the war.

Once enough incendiaries were stockpiled, the fire raids began in earnest. Warning leaflets were also dropped, which terrorized 8 million Japanese civilians into fleeing from cities. When General Carl Spaatz arrived in July to take command of U.S. Army Strategic Air Forces in the Pacific, including the Eighth Air Force redeploying from Europe, and to coordinate strategic air operations supporting the invasion of Japan, he had a directive to shift the air campaign from cities to transportation. But there was too much momentum behind the fire raids, sustained by operational tempo, training programs, and bomb stockage.

By the time Spaatz arrived, naval carrier strikes were also hitting key industrial objectives in Japan.More important, a submarine blockade had crippled the Japanese economy, the Russians were about to attack Manchuria, and Spaatz maintained direct command over the 509th Composite Group of B-29s specially modified to carry atomic bombs. Directed by Washington to deliver these weapons as soon as possible after 3 August, Spaatz ordered the attacks on Hiroshima and Nagasaki. These different elements combined with the incendiary campaign to comprise the series of blows that produced Japanese surrender.

As with the atomic bomb, there is still debate over the effects and morality of the firebombing raids. LeMay’s bombers burned out 180 square miles of 67 cities, killed at least 300,000 people, and wounded more than 400,000. His 313th Bomb Wing also sowed 12,000 mines in ports and waterways, sinking almost 1 million tons of shipping in about four months. LeMay remained convinced that his conventional bombing could have achieved victory by itself. LeMay, his tactics, and the legacy of the atomic bombs would be a primary influence in the shaping of the new United States Air Force.

References Hansell, Haywood S. Jr. Strategic Air War Against Japan. Washington, DC: U.S. Government Printing Office, 1980.

Ira Clarence Eaker

Ira Eaker and Carl Spaatz(left) were two brilliant officers whose careers intertwined, from before the famous flight of the Question Mark in 1929 to the sending of the Eighth Air Force against Germany.

Army Air Forces general.

Ira Clarence Eaker was born in Field Creek, Texas, on April 13, 1896, and in 1917 he became a pilot in the Aviation Section, Signal Corps. During January 1–7, 1929, he joined Carl A. Spaatz and Elwood Quesada on a seven-day nonstop endurance flight over Los Angeles that required 41 in-flight refuelings. In 1940 Eaker was selected to visit England and study the Royal Air Force in combat and, the following year, he received command of the 20th Pursuit Group at Hamilton Field, California. Once the United States entered World War II, Eaker gained temporary promotion to brigadier general and accompanied Spaatz to England to organize the VIII Bomber Command.

During the war, General Eaker personally led the first U.S. B-17 bomber strike against German occupation forces in France (against Rouen on 17 August 1942). As commander of the Fifteenth Air Force in the Mediterranean, he flew the first bombing raid from Italy into Germany, landing in the Soviet Union after striking a series of military targets. He advocated precision daylight bombing, a tactic that most Allied leaders were skeptical about. In addition, he also developed the plan to bomb enemy targets around the clock using U.S. B-17s to strike by day and Royal Air Force bombers to attack by night.

In the fall of 1942, Eaker replaced Spaatz as commander of the Eighth Air Force. In January 1943, during the Casablanca Conference, he personally convinced Prime Minister Winston Churchill to continue precision daylight bombing in concert with nighttime raids performed by the Royal Air Force. In June 1943 Eaker transferred to the Mediterranean, and in April 1945 Eaker returned to Washington, D.C., as deputy commanding general of the Army Air Forces, and its new chief of staff.

Before he retired from Air Force service in June 1947,General Eaker worked closely with General Spaatz and Assistant Secretary of War W. Stuart Symington to establish a separate U.S. Air Force. Awards would follow. He received the Silver Star, the Distinguished Flying Cross, and myriad other military awards from other countries as well as the United States, including a special Gold Medal from Congress in 1979.

After his Air Force retirement, General Eaker worked at the Hughes Tool Company and Hughes Aircraft until 1957. For almost two decades, he wrote a column on military affairs that was syndicated to 180 newspapers. He died in 1987, two years after President Ronald Reagan awarded him his fourth star. The wartime hero and aviation pioneer is buried at Arlington National Cemetery.