remarked that the best anti-aircraft fire-control technique would be equivalent to his bombsight, operating in reverse. Just before the Second World War, the US Navy estimated that a bomber required a 45-second run-in – defenders had no more than 45 seconds to get a fire-control solution and fire their bursts. It might take as much as 20 seconds to load and fire a gun and for its projectile to reach about 15,000ft or more. On the eve of their entry into the Second World War, US Navy anti-aircraft gunners considered level bombing the most difficult threat to counter. They may have been overly impressed by the short run-in a Norden required. The US Army bought the Norden bombsight in preference to a device it had developed, and a legend grew up about its performance and the need to maintain its absolute secrecy.25
Gyro-stabilisation made the Norden equivalent to an auto-pilot, since it controlled the bomber during its final approach to the target. Wartime US Navy Avenger torpedo bombers (TBFs and TBMs) all had Norden bombsights, which were often employed as autopilots.
Level bombing from high altitude (i.e., beyond easy anti-aircraft range) proved almost entirely ineffective during the Second World War, mainly because so much uncertainty, for example concerning wind between bomber and surface, and also because of inaccuracy in tracking targets on the surface. For example, in 1940 the Royal Navy’s Force H was repeatedly attacked by formations of Italian level bombers. It found that its anti-aircraft fire did not break them up, but it did keep them too high to accomplish much. The failure of level bombing was a great wartime surprise. The only important exception seems to have been bombing by Fw 200 Condors attacking convoys, whose merchant ships were not free to manoeuvre; the Condors apparently had excellent bomb-sights.26
Skip-bombing was an alternative. It seems to have been invented before the war by the RAF, and used from about 1940 onwards. The bomber approached at low level, and it might duck and weave as it did so. The approach ended at low altitude and at extremely short range, the bomb being dropped into the water. It was intended to skip like a rock skipped across water, to hit the side of the target ship. Once the bomb was gone, the bomber pulled up, often flying over the target ship at masthead height.
From the target’s point of view, skip bombing was not too different from torpedo attack, but the attacker was flying at much higher speed and also at somewhat greater altitude. Skip bombing was brought to the US Army Air Force in 1941 by General H H ‘Hap’ Arnold, who learned about it from the British. It may have been invented independently by General George Kenney for his Fifth Air Force in the south-west Pacific in 1943, and it was used successfully against Japanese warships and merchant ships in the 1943 battle of the Bismarck Sea.27
The British ‘bouncing’ bomb was a kind of skip bomb, a rotating object intended to hit the water and skip off to hit a distant vertical object. Because it was spinning, when it hit the vertical wall, it would descend before exploding. It was developed specifically to attack German dams. By the end of the war the British had Highball, a miniature version. At the end of the war they were working up a squadron of RAF Mosquitoes to attack the Japanese fleet in Singapore from a carrier. Highball would have bounced over torpedo nets, but it would have inflicted torpedo-like underwater damage. The war ended before the attack could be mounted.
The British seem to have been unique in developing a further kind of bombing attack, featuring the ‘B’ (buoyant) bomb. This weapon would be dropped alongside a ship. Rising in the water, it would explode below the surface, creating a shockwave which in theory might break a ship’s back. ‘B’ bombs were never used in combat, and they were all ordered destroyed in 1946. The ‘B’ bomb exemplifies anti-ship weapons which, although devastating to their targets, proved entirely impractical to deliver.28
A US B-25 Mitchell climbs out after delivering a skip-bombing attack on a Japanese freighter off New Britain, 2 November 1943. (US Office of War Information wartime release)
Air-launched rockets were the ultimate strafing weapons. This is the largest one operational during the Second World War, the 11.75in US Tiny Tim (British Uncle Tom), whose warhead was a 500lb bomb. It was powered by four standard 5in rocket motors. Initial tests failed when the blast of the motor damaged the launch aircraft. Tiny Tim was used experimentally against Japanese shipping in March 1945. Franklin and Intrepid both strongly recommended production, and Intrepid aircraft successfully fired Tiny Tims during the invasion of Okinawa in April 1945. However, the Kamikaze hit on Franklin set off Tiny Tims on her hangar deck, on board bombed-up aircraft, and they added considerably to her damage.
Dive Bombing
The most important new development in anti-ship air strike warfare between the wars was dive bombing. A form of dive bombing was developed during the First World War by several countries, notably the British. Fighters or light bombers dove at a steep angle, in effect aiming their light bombs (20 or 30lbs each). The British Fleet Air Arm continued to develop such tactics, which it called convergence attacks, after the war. The US Marine Corps became interested in this form of precision attack, presumably due to its experience in counterinsurgency in Central America and the Caribbean. Given its close connection with the Marines, the US Navy also became interested. The key US development was to heavy bombs capable of disabling aircraft carriers and sinking small warships. Not only could a dive bomber hit a manoeuvring target, it was a much more difficult target than a torpedo or level bomber flying a straight course. Attacks developed suddenly, and it appeared that fire-control systems designed to deal with level bombing could not cope. US Navy dive bombing was popularised in the 1931 movie ‘Hell Divers’, starring Wallace Beery and Clark Gable. The movie was named after the F8C-4 Helldiver dive bomber. The movie seems to have made a considerably greater impression on other navies than reports of US exercises.
The Douglas SBD Dauntless succeeded magnificently at Midway, sinking four Japanese aircraft carriers. It fought in all five carrier-vs-carrier battles in the Pacific, and many considered it superior to its successor, the Helldiver. It operated both as a scout (S) and as dive bomber (B). In the armed scout role it carried a 500lb bomb and extra fuel; in the dive-bomber role it carried a 1000lb bomb, as shown here. The Dauntless could also operate as an unarmed scout, with a range of 1445 miles, compared to 1300 miles with the 1000lb bomb. Although production ended in 1944, the Marines were still flying Dauntlesses in the Philippines when the war ended. Although it was small, the Dauntless did not fold its wings and thus occupied more deck or hangar space than its successor. BuAer never seriously considered adding the weight of a folding mechanism, because that would have cost too much fuel or bomb load. One weight it did add was an ASB (air to ship radar), which in turn required a new electrical system (this was in the SBD-4, which entered production in the autumn of 1942).
A 500lb bomb being loaded onto a US Navy dive bomber, January 1942. The cradle around the bomb is the crutch (trapeze) which swung it out so that it did not foul the propeller as it fell roughly parallel to the diving path of the aircraft.
A dive bomber had to carry added weight to deal with the stress of pulling out of its attack dive. That is why US and Japanese dive bombers in service in 1941–3 could not carry torpedoes (conversely, torpedo bombers could not handle the stresses of dive bombing). During the war a new generation of much more powerful engines made it possible to eliminate this distinction. The most prominent example was the British Barracuda, conceived as a dual-purpose dive and torpedo bomber, but used in practice as a dive bomber. The Japanese B7A Ryusei (‘Grace’) was analogous. The US Helldiver (SB2C) could carry a torpedo, but it was never used in combat for that purpose. Somewhat similarly, the Avenger
