A common belief about the 1941 Pacific Fleet was it did not value aviation; that aircraft carriers and aircraft took a back seat to battleships. After all, the 1941 Pacific Fleet was America’s last mighty battleship fleet. It even says so in the book’s title. This offers an easy explanation for the surprise at Pearl Harbor, that the battleship types had ignored the threat naval aviation posed. The US Navy’s brown-shoe aviators tacitly encouraged this belief. They profited by laying the blame on the black-shoe surface warship types. It also deflected attention from naval aviators’ failure to detect the approaching Japanese fleet until too late.

In reality the US Navy had already set its course to favor carriers over battleships by 1941. The naval aviators were firmly in charge. The US Navy’s foremost aviator, Ernest King, commanded the US Atlantic Fleet. The Navy’s most active command, it was in a de facto shooting war by summer 1941.

Admiral Ernest King reads himself in as Commander in Chief of the Atlantic Fleet on 1 February 1941. (US Navy Heritage and History Command)

By 1941 the Navy’s future construction program bet far more heavily on aircraft carriers than battleships. The Navy ordered 11 large Essex-class carriers in 1940, and two more in 1941. Plans were in hand to convert light cruisers under construction to aircraft carriers. Five of these were laid down in 1941. It commissioned the first of what would eventually become over 100 escort carriers, USS Long Island, in June 1941. Nineteen more had been laid down between 1939 and 1941.

By contrast, the Two-Ocean Navy Act of 1940 authorized procurement of only seven additional battleships. While the Navy ordered eight battleships of the Washington, South Dakota and Iowa classes between 1935 and 1940, these were intended as replacements for existing battleships, not supplements. Oklahoma, sunk at Pearl Harbor was scheduled for retirement in spring 1942. So was Arkansas, and the New York class would soon follow. The new Essex- and Independence-class carriers were to be added to the fleet while retaining the existing seven aircraft carriers. By 1940 the Navy viewed the aircraft carrier as the future.

Yet the 1941 Pacific Fleet was a battleship fleet, the US Navy’s last. When formed, it had 12 battleships and four aircraft carriers. The question, with the Navy firmly committed to the aircraft carrier, was why?

It was a matter of the US Navy cutting its coat to fit the cloth they had. The earliest the fast carriers under construction could enter service was 1943. Until then the Navy had just seven aircraft carriers. One, Hornet, would not be commissioned until October 1941. Two others, Ranger and Wasp, were relatively small, displacing less than 15,000 tons. Adequate for Atlantic distances, they were unsuited for the larger Pacific.

The four carriers assigned to the Pacific Fleet were the biggest and best in the US Navy – all that practically could be assigned to the Pacific. By contrast, the US Navy had 17 battleships, including two Washington-class ships commissioned in spring 1941. The Navy kept the three oldest commissioned battleships in the Atlantic, sending the rest to the Pacific hoping to overawe Japan.

Saratoga (foreground) and Lexington (background) along with Pennsylvania in the Canal Zone in 1934. The two carriers were two of the four carriers assigned to the Pacific Fleet when it was created. (US Navy Heritage and History Command)

In January 1941 the US thought the Imperial Japanese Navy had nine battleships, four large carriers and three or four light carriers. In theory the Pacific Fleet outnumbered the Japanese in battleships and had a rough parity in aircraft carriers. Since the Pacific was a cold theater, with no shooting while the Atlantic was the hot one, three battleships and one carrier were transferred to the Atlantic in spring 1941. This reduced the Pacific Fleet to nine battleships and three carriers, totals believed to be adequate based on intelligence estimates.

It left the US badly outnumbered. Naval intelligence was unaware that Hiei, demilitarized as a training ship in 1929, had been converted back into a battleship. This gave Japan ten battleships. Two more fleet carriers would be commissioned in fall 1941, giving Japan six, while by December 1941 Japan had seven light carriers, with two more approaching completion. It was unsurprising the 1941 Pacific Fleet failed to deter Japan, even given Royal Navy assets in Singapore.

Another misconception was that Admiral Kimmel, commanding the Pacific Fleet, pinned his hopes on a battleship engagement. He hoped to finish the Imperial Navy with a battleship action, but only at the end of a campaign. He planned to use the battleships as bait, luring the Japanese to within range of naval aviation operating from a land base.

Kimmel wanted to turn US-held Pacific atolls, like Wake Island, into major air centers using seaplanes and amphibians.

Since the US Navy was not allowed land-based multi-engine warplanes, he intended to make extensive use of the seaplane/amphibian PBY Catalina as a torpedo bomber. Unaware of the Mitsubishi Zero, he believed the slow, ungainly Catalina capable of launching daytime torpedo attacks against Japanese warships. He planned to station up to three squadrons of PBYs at atolls such as Wake or Midway. (The plan had weaknesses, discussed in the book.) Even the battleship admiral looked to naval aviation for victory.

One final note: no one, even Japan, realized the power of massed carriers. Prior to Pearl Harbor, no nation, including Japan, ever mounted a carrier operation with more than two carriers. Prior to October 1941 Japan divided its carriers two to a fleet. The number of targets at Pearl Harbor drove Yamamoto, the architect of the strike, to mass Japan’s fleet carriers into the Kido Butai (Mobile Force).

While both sides knew carrier air power would be important, neither side understood the multiplicative effect of massed carriers until the Pearl Harbor attack on 7 December 1941. (US Navy Heritage and History Command)

It turned out increasing the number of carriers in a force did not increase carrier effectiveness linearly. Rather the effect was much greater, at least multiplicative. While World War II would show two aircraft carriers working together were no more effective than two carriers operating individually, three carriers working together seemed to be as effective as five carriers operating independently. By the time nine to twelve fast carriers were massed together they could overwhelm most shore-based aviation within their reach.

That was the real lesson of the Pearl Harbor attack, one not completely digested by either Japan or the US for several years.

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