Unlike surface gunnery, anti-aircraft gunnery developed in the context of a rapidly-changing threat. There were also changes in the way in which navies evaluated the air, compared (say) to the surface, threat. There was already an air threat in 1917–18. The Germans and the British both used torpedo bombers in combat, and the British considered reconnaissance Zeppelins a major problem in the North Sea.1 Aircraft were prominent enough in anti-submarine warfare that some submarines were given heavy anti-aircraft guns. When the Royal Navy reviewed the situation in 1931–3, its Naval Anti-Aircraft Gunnery Committee cited the rise of ship-based aircraft in the US, British and Japanese navies, French flying boat operations over the Mediterranean, and the impressive mass Italian long-range flights (mainly led by Italo Balbo: the formations were often called ‘Balbos’).
Air Arms
The US Navy and the Imperial Japanese Navy both had their own air arms during the inter-war period. The US Navy became particularly air-minded. It created an instant corps of senior naval aviators by requiring all commanders of naval aviation activities and ships (including carriers) to have either ‘wings’ or aviation observer status. Ambitious officers sought the necessary training and gained an aviation perspective. The United States also created a large naval air arm, which it demonstrated to itself in the annual Fleet Problems (fleet exercises) in the Pacific. The Fleet Problems and also nearly compulsory senior officer education at the Naval War College (where the students worked out phases of the war plan against Japan) educated even non-aviators in the impact of naval aviation. For example, after one Fleet Problem in the late 1930s, the main complaint of the battleship officers was that the carriers had fought what seemed to be a private war, denying them the air services, including fighter cover, they wanted. Rear Admiral Ernest J King (Commander, Air Squadrons, Battle Force and later wartime Chief of Naval Operations) pointed out that the carriers could easily destroy each other. If they did not fight their ‘private war’, the battleships would never have any air services, because all the aircraft would be on the bottom. Typically US carriers operated well away from the battle line, which was easily spotted at a distance, in order to make it more difficult for enemy scouts to find them. That contrasted sharply with contemporary British thinking. King’s insight, which probably was widely understood, emphasised the need for anti-aircraft weapons, because at times the fleet would have to defend itself.
In support of the carrier vs. carrier war, in the late 1930s the US Navy decided that its dive bombers would have an alternative role as scouts; they were therefore designated in an SB series, as in the SBD Dauntless. US carriers typically had four squadrons on board: one of fighters, one of dive bombers, one of scouts, and one of torpedo bombers. Until the advent of radar, there was little hope that the fighters could effectively protect the carriers, which operated singly. The fighters were intended more as strike support, helping the strike aircraft deal with any defending fighters and probably also helping by strafing enemy air defence control and guns.
The pre-war Imperial Japanese Navy also had a large carrier force. Unlike the US Navy, the Japanese followed the Royal Navy (see below) in equating carrier aircraft capacity with hangar capacity.2 Typically their carriers had three rather than four squadrons on board. That is why the three US carriers at Midway had about as many aircraft as the four Japanese carriers they faced and defeated. On the other hand, in 1940–1 the Japanese succeeded in creating multi-carrier Air Fleets which could fight as single entities. Overall, they had little faith in air defence: the enemy carriers had to be destroyed before they could strike. The Japanese depended mainly on fighters rather than on shipboard anti-aircraft guns for fleet defence. However, they appear not to have appreciated the importance of fighter control, e.g. to keep fighters from being drawn entirely to counter one raid while another might be approaching. For them, Midway was an object lesson in just such failure: the defending fighters were drawn down to deal with the US torpedo bombers leaving the way open for the dive bombers. Without radar and also with poor voice radio, fighter control was impossible.
The Mitsubishi G3M (‘Nell’) made up the bulk of the Imperial Japanese Navy’s considerable land-based bomber force when the Pacific War began, and this bomber also made up the majority of the force which sank Prince of Wales and Repulse. The object under the belly of this ‘Nell’ is the rack for a torpedo or bombs. (Phil Jarrett)
The most important factor in air operations against ships is that the sea is so broad. Air attacks cannot be mounted until the enemy is found. That is why signals intelligence was so important in the Second World War: when it worked, it showed the attacker where to search. Operations in narrow waters were of course simpler, but they always required search before attack. The Japanese used shipboard floatplanes to find enemy fleets. In 1942 the Japanese naval staff tried an alternative, the high-performance carrier aircraft shown here. This C6N1 Saiun (‘Myrt’) was designed to a Spring 1942 specification requiring a maximum speed of 350kts and a range of 1500nm at 210kts (maximum 2500nm). The Saiun flew in May 1943 and was accepted even though it did not achieve the desired speed. During the battle of the Philippine Sea, Saiuns effectively shadowed the US fleet, their high speed protecting them from interception. They were responsible for the great success the Japanese enjoyed: they were able to attack from well beyond the attack range of the US fleet. That did them little good, because US fighter control and US anti-aircraft guns were so effective. This ‘Myrt’ was captured on Saipan in June 1944.
The wartime successor to ‘Nell’ was the G4M (‘Betty’), which, like its predecessor, could deliver both bombs and torpedoes. G4Ms were part of the attack against Repulse and Prince of Wales, and later in the war they executed effective night torpedo attacks against US carriers and cruisers. At the end of the war they launched Okha manned stand-off missiles. (Philip Jarrett)
Like their US counterparts, Japanese cruisers carried floatplanes assigned to scouting as well as spotting duties. In the US Navy, the floatplane scouts were intended for use when the cruiser or cruisers operated independently, far from the fleet. Unlike the US Navy, the Japanese used these same floatplanes to scout for carriers screened by the cruisers, as at Midway. Wartime US and British observers considered that the problems of tracking enemy fleet units and of coaching a strike force into position had received particular attention in the Imperial Japanese Navy.3 Scouting was considered so important that, unlike the US Navy, the Japanese separated it from strike, to the extent that scouts were ordered to avoid combat if possible so that they could complete their scouting missions. The fleet scouting mission was symbolised by the design of the Tone class cruisers, with their open aircraft areas aft. Only during the war did the Japanese develop a specialised high-performance carrier scout, the C6N1 Saiun.4 It had no Western equivalent. Wartime Japanese air tactics envisaged a scout or snooper working with a strike force, using elaborate tracking and liaison techniques. By 1943–4 Japanese scouting aircraft had radar. They were advised to minimise both radar and radio transmissions until the moment came to home the strike force on the target, at which time there had to be a considerable volume of traffic to and from the tracking aircraft. On this basis communications volume became a reasonable indication that a striking force or a relief shadower was being homed on the target.
Japan was unique in having both a carrier air arm and a substantial naval land-based air arm. The US Navy also had a large shore-based air arm, but it consisted of flying boats, not high-performance bombers like the G3M ‘Nell’ and its successor G4M (‘Betty’). ‘Nell’ was built to a requirement conceived in 1933 by Admiral Yamamoto, who was then chief of the technical division of the Japanese Naval Bureau of Aeronautics (the equivalent of the US Navy’s BuAer). Admiral Yamamoto was aware of developments which gave twin-engine aircraft very high performance (which in Britain was taken to mean that ‘the bomber will always get through’)