That wasn’t known in 1941. Carriers were for scouting for the battle line. They only became critical in the Pacific after the Japanese sank our battle line. In the Atlantic, they were never important, The Germans, Italians and British still considered the battleships and cruisers the most important ships in the fleet.
The British had started the concept of an aircraft carrier before anyone else and they were expecting them to have more value in the next war (World War Two).
Germany had started production of an aircraft carrier but it was cancelled half complete in 1940.
France and Italy had less global plans for their fleets and weren't convinced on the need for aircraft carriers.
The USA had seven aircraft carriers at time of the Pearl Harbor attack, but had embraced their role as more than scouting long before the start of WWII.
...
After the abrogation of disarmament treaties by Japan in 1936, the U.S. took a realistic look at its naval strength. With the
Naval Expansion Act of Congress passed on 17 May 1938, an increase of 40,000 tons in aircraft carriers was authorized. This permitted the building of
Hornet, which was the third
Yorktown-class carrier, and
Essex, which was the
lead ship of a new class.
CV-9 was to be the prototype of the 27,000-ton (standard displacement) aircraft carrier, considerably larger than
Enterprise, yet smaller than
Saratoga (a
battlecruiser converted to a carrier). The Navy ordered the first three of the new design,
CV-9,
CV-10 and
CV-11, from
Newport News Shipbuilding & Drydock on 3 July 1940. These were to become known as
Essex-class carriers.
[5] Under the terms of the
Two-Ocean Navy Act, eight more of these carriers were programmed. Eight were ordered on 9 September, CV-12 through −15 from Newport News, and CV-16 through −19 from
Bethlehem Steel's
Fore River Shipyard; the last two,
CV-20 and
CV-21, were authorized 23 December 1941,
[6] with the primary intention of keeping existing slipways busy,
[7] and were ordered eight days after
Pearl Harbor from the
Brooklyn Navy Yard and Newport News respectively.
...
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