Did the Japanese plan a second attack on Pearl Harbor on New Year's, right after their first attack on Dec. 7, 1941?
Japanese documents captured by the United States at the end of World War II and just turned over to the National Archives by the super-secret National Security Agency strongly suggest that a second attack was on the drawing board.
The documents indicate that a Japanese submarine force planned to attack the ships still at anchor in Pearl Harbor on the night of New Year's Eve, a little more than three weeks after the first Pearl Harbor attack devastated the U.S. Pacific Fleet.
One document is a cable dated Dec. 27, 1941, to commanders of Japanese submarines at sea in the Pacific, giving them the number and size of U.S. Navy ships then at anchor in Pearl Harbor.
Others are cables sent Dec. 26 and 29 by the commander of Japan's First Submarine Force, directing three of Japan's largest submarines to rendezvous off the east and west coasts of the main Hawaiian island of Oahu and attack American ships two days later.
Nowhere among subsequent cables is there any indication why the attack was not carried out, nor why Japanese submarines never attacked American ships coming in and out of Pearl Harbor in the early months of the Pacific war.
Naval historians have long wondered why the Japanese did not send their submarines to the environs of Hawaii to attack American shipping. There was not a single Japanese submarine attack reported on any U.S. ship entering and leaving Pearl Harbor in the weeks and months following the Dec. 7 attack.
The cables turned over to the Archives reveal that at least five of Japan's largest submarines were dispatched to the West Coast of the United States in December, 1941, and January, 1942.
There was only one known shelling of the California coast by a surfaced Japanese submarine. Early in 1942 a Japanese submarine surfaced at night off the coast of Santa Barbara and fired half a dozen shells at the southern California city.
While the cables give no explanation of why the submarine attack was not carried out at Pearl Harbor, they explain why Japanese submarines did not attack more West Coast cities.
Cables to Tokyo naval headquarters from the submarine commanders reveal that they had trouble navigating in the cold, swift Pacific Ocean currents off the U.S. West Coast.
The cables also reveal that the Japanese submarines were equipped with periscopes that could rise only about 20 feet above their conning towers. Submarine commanders complained that their periscope depth was so shallow it did not give them enough water to evade American destroyers and patrol planes along the California coast.
"Suggest new submarines be fitted with longer periscopes," one cable from a Japanese submarine commander reads, "to allow deeper running depth."