I was reading the Wikipedia page on the Two-Ocean Navy Act (1940) which focused production on carriers at the expense of battleships. Rep. Vinson said, "The modern development of aircraft has demonstrated conclusively that the backbone of the Navy today is the aircraft carrier. The carrier, with destroyers, cruisers and submarines grouped around it[,] is the spearhead of all modern naval task forces."
How did Vinson know this in 1940? I was under the impression that carriers only gained supremacy in the eyes of policymakers and leaders after Pearl Harbor, Coral Sea, and Midway. Clearly Vinson already considered battleships inferior to carriers before those engagements and the evidence was sufficient for a unanimous vote by the House to approve the act. What evidence existed at the time?
If an American concluded that carriers would be the backbone of naval power before the British raid on Taranto in November of 1940, one must immediately think first of Billy Mitchell. Mitchell was successful in demonstrating the ability of aircraft to sink battleships, and they still wanted to court martial him for his views.
Putting both Vinson and Mitchell together in a search brings up the Morrow Board, called to examine the relevance of aviation to reduce the political fallout of going after Mitchell. Vinson was the congressman devoted to naval aviation on the board, and afterwards he was a supporter of a strong carrier force. So, obviously Mitchell's arguments didn't entirely fall on deaf ears.
First attempt at a top level comment, if it is underwhelming the moderators should feel free to remove it.
Both the United States Navy and the Imperial Japanese Navy had significant numbers of officers who felt that carriers should be the centerpiece of naval power well before war broke out in the Pacific.
A lot of them are actually quite well known: Since they were in the carrier business, a lot of them leapfrogged their big-gun counterparts when the carrier did finally and conclusively demonstrate it's superiority.
The most prominent US example is Halsey; he went to flight school after the age of 50 to earn his wings and with them eligibility for a carrier command.
On the Japanese side the best known might be JisaburÅ Ozawa, Commander in Chief of the Combined Fleet later in the war, who was an enthusiastic advocate of naval air power. That the politics of promotions placed Nagumo (very much a member of the "gun club") as commander of the carrier striking force rather than Ozawa was an unhappy occurrence for Japan, as it turned out.
What this has to do with Vinson is that it shows that the carrier didn't suddenly emerge from nowhere to become the primary naval weapon* over the approximately twenty months between Taranto and Midway, but rather settled a debate that had been ongoing for the better part of a decade. It should not be at all surprising that a Congressman closely associated with the Navy might have been on the side of the aviators, especially as late as 1940.
*In my purely personal opinion, this angle is played up in many history books simply because it is dramatic.
I can't speak exactly to how he "knew", but I can say say that in the context of the time a lot of top military brass thought the Navy was obsolete with the coming of the military airplane. This statement may show a lot of foresight, but it could also be Vinson attempting to speak to the "culture" of the time in order to keep the Navy relevant.
Source: Bluejacket's Manual
I think it's Bad History that the Navy was still battleship centric by 1940. There was certainly still inertia for battleships, as proved by the design and operation of three new classes of battleship from 1941 (North Carolina commissioned in 1941) to 1944 (Missouri commissioned in 1944). However, the high speed they were designed for starting in was specifically so that they could operate with US Fleet carriers U.S. Aircraft Carriers: An Illustrated Design History - Norman Friedman, P. 122 and this design had started back in 1935.
The Navy had run a series of exercises known as fleet problems between 1923 and 1940 that were intended to test new theories as well as train the fleet. Fleet Problem XIII in 1932 saw a prelude to the attack on Pearl Harbor when the attacking force used carriers and cruisers (leaving assigned battleships behind) to dash in and attack the defending force in the early morning, "sinking" the defending fleet.
A "lesson learned" issued by the commander of that attacking force Rear Admiral Yarnell after the exercise was that fleets in these operations tended to focus on eliminating the other side's carriers first, which pretty much indicates that even then early high-ranking Navy officials knew where the crucial power in a fleet was.
Vinson had long-time connection to the Navy, joining the House of Representatives Naval Affairs Committee shortly after the end of the First World War and maintaining that connection well past the end of the war. So, he would have been exposed to most of these lessons and theories by the Naval officers he came in contact with and collaborated with. It's not a surprise that he was such a proponent for aircraft carriers or that one was named for him.