The reaction of the United States was outrage at this undeclared act of war, and the United States declared war on Japan the next day. Three days later, Hitler and Mussolini declared war on the United States, making the conflict truly a world war. At the time of Pearl Harbour, the U.S. aircraft carrier fleet was out on manoeuvers and thus escaped attack.

However, the effect of the Pearl Harbour attack was to bring the United States and Japan into a closer state of military parity. Although the attack, and the December 13 attack on the U.S. airfields in the Philippines (which somehow also came as a surprise), gave Japan the momentary edge, and the United States would be involved in a theatre of war on the other side of the globe, the industrial output of the United States would clearly make up the shortfall in a year or so.

The strategy of the Japanese government in 1941, as it had been twice before in the century, was to fight a limited war until it gained its objectives, and then dig in. The attacks on Pearl Harbour and the Philippines were designed to buy the time needed to create new boundaries in the Pacific.

That the war turned into a contest to the death was due in part to the unwillingness of the Japanese military and the American political leadership to think in such equivocal terms. The  fighter aircraft that Japan used to achieve early control of the skies were, as has been pointed out, derived from American and British designs (the Germans were much more circumspect about sharing their technology with their Japanese allies), but the designers at the chief manufacturers—Aicihi, Kawanishi, Kawasaki, Mitsubishi, and Nakajima—took those ideas and pushed then in new directions that astounded aircraft designers the world over.

Moreover, unlike the Germans, the Japanese kept developing their aircraft and creating innovative designs. In fact, sometimes new models of older fighters (like the A6M3, a new model of the A6M) were given new designations because they looked like new airplanes even to trained observers.

The greatest of these fighters, on a par with the Spitfire and the Bf 109, was the Mitsubishi A6M Reisen, identified officially by the Allies as “Zeke,” but known throughout the war as the Zero. The Zero had a manoeuvrability that seemed physically impossible to American  pilots; finding its weakness became a top priority.

Painstakingly (and sometimes heroically), pieces of downed Zeros were recovered and brought to Wright Field in Day ton, Ohio, and pieced together. The engineers found that the engine was  modelled on an old Pratt & Whitney that had been abandoned because of difficulty it had in diving, and that the plane had virtually no protective armour. The strategy developed for fighting Zeros was to avoid engagements at close range, to attack from above, forcing it to dive, its most vulnerable flight phase, and to use wide-area explosives that would disable the aircraft with even a glancing hit.

The key to the defeat of the Japanese air force was not in the tactics used against the Zero, but in the limited capacity of Japan to manufacture planes to replace those downed. Of the five important Japanese fighters deployed during the war, the Zero was produced in the greatest numbers, but production reached only about 10,500.

The Hayate was seen by experts as the best Japanese fighter of the war. In May and June of 1942, two battles, fought at great cost to both sides, marked the turning points in the war:  the Battle of the Coral Sea (fought May 2-8) and the Battle of Midway (fought June 4-.7). Both were called naval battles, but they were fought by ships that never saw one another and never, in fact, fired directly on an enemy naval vessel. In both battles, the objectives were very similar: the Japanese were seeking a foothold that would allow them to isolate Australia from the American fleet, and the Allies were determined to stop them.

Scene on board USS Yorktown (CV-5), shortly after she was hit by three Japanese bombs on 4 June 1942. Dense smoke is from fires in her uptakes, caused by a bomb that punctured them and knocked out her boilers

Both battles ended with the Japanese being forced to retreat, but whereas the Japanese claimed victory at the Battle of the Coral Sea because the Americans sustained greater losses, no such claim was possible at Midway. The Japanese lost four aircraft carriers and more than 330 aircraft to the Americans’ losing only the Yorktown and 150 aircraft. Midway was also the first battle for the CV 6 Enterprise, a name that  was to become synonymous with excellence in naval aviation.