Article: Battle of Midway
Section: Impact

Question: What was the reason the shipbuilding program mandated by Second Vinson Act was created?

The Battle of Midway has often been called "the turning point of the Pacific".
However, the Japanese continued to try to secure more strategic territory in the South Pacific, and the U.S. did not move from a state of naval parity to one of increasing supremacy until after several more months of hard combat.
Thus, although Midway was the Allies' first major victory against the Japanese, it did not radically change the course of the war; instead it was the cumulative effects of the battles of the Coral Sea and Midway that reduced Japan's ability to undertake major offensives.
In addition Midway paved the way for the landings on Guadalcanal, and the prolonged attrition of the Solomon Islands campaign, both of which finally allowed the Allies to take the strategic initiative and swing onto the offensive for the rest of the Pacific War.
Finally, Midway bought the United States valuable time until the first of the new "Essex"-class fleet carriers became available at the end of 1942.
The battle also showed the worth of pre-war naval cryptanalysis and intelligence-gathering.
These efforts continued and were expanded throughout the war in both the Pacific and Atlantic theaters.
Successes were numerous and significant.
For instance, Navy cryptanalysis made possible the shooting down of Admiral Yamamoto's airplane.
Some authors have stated heavy losses in carriers and veteran aircrews at Midway permanently weakened the Imperial Japanese Navy.
Parshall and Tully, however, have stated that the losses in veteran aircrew, while heavy (110, just under 25% of the aircrew embarked on the four carriers), were not crippling to the Japanese naval air-corps as a whole: the Japanese navy had some 2,000 carrier-qualified aircrew at the start of the Pacific war.
A few months after Midway, the JNAF sustained similar casualty rates at both the Battle of the Eastern Solomons and Battle of Santa Cruz, and it was these battles, combined with the constant attrition of veterans during the Solomons campaign, which were the catalyst for the sharp downward spiral in operational capability.
However, the loss of four large fleet carriers, and over 40% of the carriers' highly trained aircraft mechanics and technicians, plus the essential flight-deck crews and armorers, and the loss of organizational knowledge embodied by such highly trained crew, were heavy blows to the Japanese carrier fleet.
After the battle and were the only large carriers of the original Pearl Harbor strike-force left for offensive actions.
Of Japan's other carriers, , which was not commissioned until early 1944, would be the only fleet carrier worth teaming with "Shōkaku" and "Zuikaku"; and "Zuihō" were light carriers, while and , although technically classified as fleet carriers, were second-rate ships of comparatively limited effectiveness.
By the time of the Battle of the Philippine Sea, the Japanese had somewhat rebuilt their carrier forces in terms of numbers, but their planes, which by then had become obsolescent, were largely flown by inexperienced and poorly trained pilots.
In the time it took Japan to build three carriers, the U.S. Navy commissioned more than two dozen fleet and light fleet carriers, and numerous escort carriers.
By 1942 the United States was already three years into a shipbuilding program mandated by the Second Vinson Act, intended to make the navy larger than Japan's.
The greater number of USN aviators survived the Battle of Midway and subsequent battles of 1942, and combined with growing pilot training programs, the US accumulated a large number of skilled pilots to complement its material advantages in ships and planes.