Events Leading To The Attack On Pearl Harbor - Lack of Preparation

Lack of Preparation

U.S. civil and military intelligence had, amongst them, good information suggesting additional Japanese aggression throughout the summer and fall before the attack. At the time, no reports specifically indicated an attack against Pearl Harbor. Public press reports during summer and fall, including Hawaiian newspapers, contained extensive reports on the growing tension in the Pacific. Late in November, all Pacific commands, including both the Navy and Army in Hawaii, were separately and explicitly warned war with Japan was expected in the very near future, and it was preferred that Japan make the first hostile act as they were apparently preparing to do. It was felt that war would most probably start with attacks in the Far East: the Philippines, Indochina, Thailand, or the Russian Far East. The warnings were not specific to any area, noting only that war with Japan was expected in the near future and all commands should act accordingly. Had any of these warnings produced an active alert status in Hawaii, the attack might have been resisted more effectively, and perhaps resulted in less death and damage. On the other hand, recall of men on shore leave to the ships in harbor might have led to still more being casualties from bombs and torpedoes, or trapped in capsized ships by shut watertight doors (as the attack alert status would have required), or killed (in their obsolete aircraft) by more experienced Japanese aviators. When the attack actually arrived, Pearl Harbor was effectively unprepared: anti-aircraft weapons not manned, most ammunition locked down, anti-submarine measures not implemented (e.g., no torpedo nets in the harbor), combat air patrol not flying, available scouting aircraft not in the air at first light, Air Corps aircraft parked wingtip to wingtip to reduce sabotage risks (not ready to fly at a moment's warning), and so on.

By 1941, U.S. signals intelligence, through the Army's Signal Intelligence Service and the Office of Naval Intelligence's OP-20-G, had intercepted and decrypted considerable Japanese diplomatic and naval cipher traffic, though nothing actually carrying significant information about Japanese military plans in 1940-41. Decryption and distribution of this intelligence, including such decrypts as were available, was capricious and sporadic, some of which can be accounted for by lack of resources and manpower. At best, the information available to decision makers in Washington was fragmentary, contradictory, or poorly distributed, and was almost entirely raw, without supporting analysis. It was thus, incompletely understood. Nothing in it pointed directly to an attack at Pearl Harbor, and a lack of awareness of Imperial Navy capabilities led to a widespread underlying belief Pearl Harbor was not a possible attack target. Only one message from the Hawaiian Japanese consulate (sent on 6 December), in a low level consular cipher, included mention of an attack at Pearl; it was not decrypted until 8 December.

In 1924, General William L. Mitchell produced a 324-page report warning that future wars (including with Japan) would include a new role for aircraft against existing ships and facilities. He even discussed the possibility of an air attack on Pearl Harbor, but his warnings were ignored. Navy Secretary Knox had also appreciated the possibility of an attack at Pearl in a written analysis shortly after taking office. American commanders had been warned that tests had demonstrated shallow-water aerial torpedo attacks were possible, but no one in charge in Hawaii fully appreciated this. And a war game surprise air raid against Pearl Harbor in 1932 led by Admiral Harry E. Yarnell had been judged a success and to have caused considerable damage, a finding corroborated in a 1938 war game by Admiral Ernest King.

Nevertheless, because it was believed Pearl Harbor had natural defenses against torpedo attack (e.g., the shallow water), the Navy did not deploy torpedo nets or baffles, which were judged to inconvenience ordinary operations. And as a result of limited numbers of long-range aircraft (including Army Air Corps bombers), reconnaissance patrols were not being made as often or as far out as required for adequate coverage against possible surprise attack; they improved considerably, with far fewer remaining planes, after the attack. The Navy had 33 PBYs in the islands, but only three on patrol at the time of the attack. Hawaii was low on the priority list for the B-17s finally becoming available for the Pacific, largely because General MacArthur in the Philippines was successfully demanding as many as could be made available to the Pacific (where they were intended as a deterrent). The British, who had contracted for them, even agreed to accept fewer to facilitate this buildup. At the time of the attack, Army and Navy were both on training status rather than operational alert.

There was also confusion about the Army's readiness status as General Short had changed local alert level designations without clearly informing Washington. Most of the Army's mobile anti-aircraft guns were secured, with ammunition locked down in armories. To avoid upsetting property owners, and in keeping with Washington's admonition not to alarm civil populations (e.g., in the late November war warning messages from the Navy and War Departments), guns were not dispersed around Pearl Harbor (i.e., on private property). Additionally, aircraft were parked on airfields to lessen the risk of sabotage, not in anticipation of air attack, in keeping with Short's interpretation of the war warnings.

Chester Nimitz said later, "It was God's mercy that our fleet was in Pearl Harbor on December 7, 1941.". Nimitz believed if Kimmel had discovered the Japanese approach, he would have sortied to meet them. With the American carriers absent and Kimmel's battleships at a severe disadvantage to the Japanese carriers, the likely result would have been the sinking of the American battleships at sea in deep water, where they would have been lost forever with tremendous casualties (as many as twenty thousand dead), instead of in Pearl Harbor, where the crews could easily be rescued, and six battleships ultimately raised.