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USS Coral Sea (CV-43)The armoured flight deck debate is nothing new. It is one that has raged back and forth since the 1930s. The USN, in particular, put enormous effort into understanding the concept’s strengths and weaknesses.The pre-war USN was intrigued by the potential of armoured flight decks. But it was hesitant about the trade-offs it entailed.Time and again the US Navy’s Fleet Problem exercises revealed that carriers were immensely vulnerable.It wasn’t so much a matter of strike size. It was a matter of who got in the first strike. Even lightly damaged carriers never had a chance to launch a counterstrike.This became the nexus of decades of debate.Larger, protected ships (such as Lexington and Saratoga) could individually carry large numbers of aircraft while having some ability to withstand attack. But few such ships could be built under the Washington Treaty’s tonnage ceiling.Smaller, lighter ships (such as Ranger) could be deployed in groups and get large combined strikes of aircraft into the air quickly. Individually, though, each ship was very vulnerable.It was the same problem the RN had uncovered during its own manoeuvres.Both navies were faced with a quandry: Would greater numbers of smaller flight decks mean enough capacity for a winning counterstrike? Or would a more heavily protected fleet carrier be able to sustain effective operations after taking a measure of damage?“Given the tonnage ceiling, however, carriers with either armoured or unarmoured flight decks were a gamble,” Hone, Friedman and Mandeles write in American & British Aircraft Carrier Development. “Any design was risky, because the Washington and London treaties forbade navies from building an operational carrier that could be experimented with and then thrown away if the experiment failed. As a result, Navy carrier commanders were still arguing about the value of carriers with armoured flight decks as late as 1939.” The armoured flight deck debate is nothing new. It is one that has raged back and forth since the 1930s. The USN, in particular, put enormous effort into understanding the concept’s strengths and weaknesses.View fullsize DOCTRINE DICHOTOMY“The carrier whose planes are not protected while on board is in precisely [the same] situation [as] a main battery gun mounted on the open deck with unprotected ammunition around it.— Captain John S. "Slew" McCain, USS RangerThe pre-war USN was intrigued by the potential of armoured flight decks. But it was hesitant about the trade-offs it entailed.Time and again the US Navy’s Fleet Problem exercises revealed that carriers were immensely vulnerable.It wasn’t so much a matter of strike size. It was a matter of who got in the first strike. Even lightly damaged carriers never had a chance to launch a counterstrike.This became the nexus of decades of debate.Larger, protected ships (such as Lexington and Saratoga) could individually carry large numbers of aircraft while having some ability to withstand attack. But few such ships could be built under the Washington Treaty’s tonnage ceiling.Smaller, lighter ships (such as Ranger) could be deployed in groups and get large combined strikes of aircraft into the air quickly. Individually, though, each ship was very vulnerable.It was the same problem the RN had uncovered during its own manoeuvres.Both navies were faced with a quandry: Would greater numbers of smaller flight decks mean enough capacity for a winning counterstrike? Or would a more heavily protected fleet carrier be able to sustain effective operations after taking a measure of damage?“Given the tonnage ceiling, however, carriers with either armoured or unarmoured flight decks were a gamble,” Hone, Friedman and Mandeles write in American & British Aircraft Carrier Development. “Any design was risky, because the Washington and London treaties forbade navies from building an operational carrier that could be experimented with and then thrown away if the experiment failed. As a result, Navy carrier commanders were still arguing about the value of carriers with armoured flight decks as late as 1939.” Three generations of US carrier doctrine … USS Saratoga, Enterprise, Hornet, and San Jacinto, in September 1945Three generations of US carrier doctrine … USS Saratoga, Enterprise, Hornet, and San Jacinto, in September 1945THE BIG-STRIKE The ultimate effectiveness of the ‘big strike’ concept cannot be denied. Swarms of powerful carrier-launched aircraft simply overwhelmed Japanese defences in 1945.Proponents of the concept were vindicated. Many felt decades of “black shoe” (gun-based) thinking had restrained the inevitable ascendancy of “brown shoe” naval aviation.But, as Hone, Friedman and Mandales point out, things are never that simple.The ‘big strike’ was simply not possible before 1944.Carrier strikes represented a ‘pulse’ of offensive firepower. It took time to build up, deploy, coordinate and deliver this pulse. Then it had to find its way safely home. During this time, the enemy could well be doing the same.In the 1930s and early 1940s, no carrier group could both defend itself and strike at the same time. “Under actual war conditions it is quite possible that all of the carriers engaged … (will be) lost or put completely out of action,” CinC US Fleet noted of Fleet Problem XV in 1934. “With opposing air forces of equal efficiency this is by no means an impossible result of the opening movements of a naval campaign.”The only option was to find the enemy first, and get in the first strike.In Fleet Problem XX of 1939, USS Ranger was able to locate USS Enterprise through radio direction finding. Ranger’s aircraft ‘destroyed’ Enterprise without the latter having any time to put up an effective defence.All this cemented the perception that carriers were inherently vulnerable. Worse so even than World War I’s battlecruisers. “Eggshells with hammers” had a new application.The value of weapons without any real chance of surviving long in a war was a real question.And while massed carrier forces were possible, key engineering and logistic challenges had yet to be identified and solved. Such as the provision of a large fleet train of support ships carrying aviation fuel, ammunition, replacement aircraft and crew. Then there were the aircraft themselves. Their performance was poor. Endurance was limited - especially with bomb loads. Finding targets was immensely problematic. Not to mention navigating back to a flight deck that was nowhere near where it had been when they took off.These challenges were only fully overcome in 1944. Aircraft such as the Hellcat, Corsair and Avenger had the necessary performance to meet the demands placed upon them. And they were well supported by the radar direction, navigation aids and an immense supply chain needed to put them on target.