CONCEPT: Prewar US design emphasized offensive over defensive qualities as had those of the Royal Navy prior to the First World War. However, whereas this had proved a less than successful policy in Britain's navel war against Germany it resulted, mainly by good judgment but partially by luck, in a close to ideal group of ships for the war against the Japanese. In aircraft carrier development this manifested itself in the provision of ships in which a large air group and its efficient operation took priority over passive defense. The logic behind this was that the aircraft were both the carrier's principal means of offensive and defense and if operated efficiently few if any enemy aircraft would reach the ship itself and even then they would have to penetrate the ship's AA barrage before they could inflict any damage. Thus the hull was provided with sufficient armor and water-tight subdivision to ensure survivability under all but the severest of circumstances but the remainder of the ship - that is everything above the main deck, which included her hangar and flight deck - were completely unprotected apart from the splinter plating applied to the bridge and gun positions.
The alternative system was that employed by the Royal Navy in the Illustrious class in which the flight deck and hangar were armored but, on a given displacement, this degree of protection could only be achieved by a considerable sacrifice in the air group - US prewar doctrine required carriers with hangar accommodation for 72 aircraft, whereas the Illustrious class carried 36. It had its effect on carrier operation as well for while US carriers with their open hangars could start and warm up aircraft engines while they were still in the hangar, and thus speed up the rate of launch, this was not possible with a closed hangar.
Thus a large air group meant accepting the risk of a carrier being put out of action by damage to her flight deck or hangar. This proved a greater risk than imagined prewar, at which time it was assumed that any bomb hole in the comparatively light flight deck could easily be repaired aboard ship. This was in fact the case with some of the less severe instances of damage but it did not take account of the inherent vulnerability of the hangar contents - aircraft, their gasoline, and munitions - and in many case US carriers suffered severely from fires and secondary explosion caused by a bomb or kamikaze hit. In this respect the kamikaze proved to be the most dangerous weapon used against the Essex class, although it was a form of attack that could not, of course, have been envisaged at the design stage. Being virtually a piloted bomb it stood a high chance of success but fortunately aircraft have poor penetrating power and thus were normally stopped by the flight deck - although their bombs, and occasionally their engines, penetrated to the hangar. Intrepid herself was hit by kamikazes on three occasions, two of which resulted in severe damage and her retirement from action for extensive repairs. However, the alternative to the Essex design, the following Midway class, which had a 3.5" armored flight deck and to be fair many other improvements including a larger air complement, displace 47,000 tons, nearly twice the tonnage of the previous class.