When the massive hulls of battlecruisers Lexington (CC-1) and Saratoga (CC-2) were designated to be completed as aircraft carriers under provisions of the 1922 Washington Treaty, they represented a multi-generational leap forward for aircraft carrier design. Eight hundred and eighty-eight feet long and displacing more than 44,000 tons loaded, these sleek monsters were capable of 33+ knots (some tales that Sara and Lex reached 40 knots during Fleet Problems in the late 1930s have never been verified) and could carry almost ninety aircraft.
They were, in fact, far more modern in the 1920s than the fragile and short-range airplanes they carried. Other than the mammoth IJN Shinano (built on the hull of the third Yamato), which never operated with aircraft, Lexington and Saratoga were the largest aircraft carriers built until the Midways entered service post-war. They were 12 knots faster than the battle fleet, and potentially capable of powerful, far-ranging strikes not conceived of before they entered service.
The design of Lex and Sara was still largely experimental, and contained some oddities that time and experience would either correct or eliminate. Famously, these two aircraft carriers were armed with a heavy cruiser’s guns. Each carried eight 8-inch/55 caliber Mk IX naval rifles in specially contrived twin mounts. The gun housings lacked armor, consisting of little more than splinter shields, in order to save topside weight. (While the mounting of heavy caliber guns seems in retrospect an anachronism, doubts about the ability of aircraft to actually engage and sink surface ships who might cross paths with the carriers were well founded in the early 1920s. Despite Billy Mitchell’s experiments, the age of dominance of air power had not yet arrived for the world’s navies. Indeed, the loss of HMS Glorious in 1940 and the sinking of three more aircraft carriers by gunfire over the course of the war might give more justification to the heavy main battery than commonly believed.) The aligning of the centerline of the flight deck with the hull centerline was discovered to necessitate significant ballast to port to offset the weight of the island. All future designs, starting with Ranger (CV-4) would have the appropriate offset of flight deck centerline on the hull.
Both vessels were given what was for the time a massive anti-aircraft battery. Twelve of the new 5″/25 caliber Mk 10 AA guns were fitted, six on each side in single mounts, and controlled by the then-state of the art Mk 19 director. A number of .50 (12.7mm) caliber machine guns installed in 1929 comprised the sole light AA capability. As the size, speed, and lethality of carrier aircraft increased through the 1930s, however, it was soon clear that the .50 caliber machine guns were of dubious utility, and the development of the heavier 1.1″ (27.6mm) quad mount machine guns began. Design delays in the 1.1″ AAMG were the impetus for the mounting of a number of 3″/50 caliber AA cannon until the design was ready for fielding, which occurred in early 1941. The 1.1″ AAMG turned out to be a mixed bag. When working properly, the 1.1″ proved effective in action, but maintenance and reliability issues, and the obvious requirement for a heavier projectile in the AA role against modern aircraft, led to the shipping of the famous twin and quad 40mm Bofors AA cannon beginning in mid-1942 on most US warships.
However, that decision was still in the future when plans were drawn up in 1940 to modernize Lexington and Saratoga as Pacific war clouds gathered. It was planned to remove the 8″/55 Mk IX mounts on both vessels, and replace them with four twin Mk 12 mounts carrying the highly effective 5″/38 caliber dual purpose gun mated to Mk 37 gun directors, two mounts per director. The 5″/38 was more accurate than its predecessor, and had an effective ceiling of 37,200 feet, 10,000 feet higher than the 25 caliber gun. In addition, the plans called for the replacement of the elderly Mk 19 directors, first developed in 1925, with the newer Mk 33. The Mk 19 was incapable of computing for dive bombing, and was almost entirely ineffective at tracking 250-knot aircraft now fielded by the Japanese, further restricting the effectiveness of the 5″/25 to under 17,000 feet.
The coming of war in December of 1941 meant that Lexington would be a desperately needed asset, and indeed she was active for the first four months in the Pacific war as a part of Task Force 11. During a brief refit in late-March, 1942, Lexington’s 8″/55 mounts were landed, but the Mk 12 5″/38 mounts (and Mk 37 directors) to replace them were not installed, as Lexington was desperately needed in the fight against the Japanese Navy. In addition, the Mk 33 directors destined for the older 5″/25 batteries were likewise not fitted. In place of the planned 5″/38s, a temporary installation of more 1.1″ AAMGs and some 20mm Oerlikon cannon was instead completed.
Photographs of Lexington as she steamed into the Battle of the Coral Sea are noteworthy for the absence of her familiar 8″/55 mounts, and omission of the 5″/38 mounts which Saratoga would receive while being repaired from torpedo damage a couple of months later. What Lexington was left with for anti-aircraft defense was a heavy battery of older 5″/25 guns whose effectiveness was hampered by outdated fire control, and light AA in insufficient numbers to effectively defend her. Whether this made any difference in the loss of Lexington is anyone’s guess, but the possibility certainly exists. The mating of the 5″/38 with the Mk 37 director was the most lethal anti-aircraft combination to go to sea in World War II. Perhaps such a combination could have caused the Japanese torpedo and dive bombers who fatally struck Lexington on 8 May 1942 to have missed, or might have destroyed them before they struck the ship. What is indisputable, however, is that Lexington was sent into action against a modern and capable enemy with equipment and weapons that were known to be obsolete and lacking in combat effectiveness. Operational tempo had restricted the US Navy’s ability to sufficiently modernize a capital ship to acceptable standards to meet the requirements of combat at sea. Despite the very recent rapid expansion undertaken in America’s shipyards, the United States went to war in the first six months in the Pacific with the Navy it had, not the one it would require to fight and win.
There is a lesson in there, somewhere.