On December 7, 1941, the American naval base at Pearl Harbor, Hawaii, suffered a surprise but coordinated attack by Japanese forces. In less than two hours, World War II took a new turn, which would shape events across the globe.
Overall, the attack claimed the lives of over 2,400 Americans, while more than 300 aircraft and numerous ships were destroyed or severely damaged. For Japan, the operation was considered a tactical success, but it would soon prove strategically fatal.
The United States declared war on Japan, officially entering World War II. A few days later, Germany and Italy declared war on the U.S., turning the conflict into a fully global war.
TO VIMA, December 6, 1981, shortly before the 40th anniversary of the attack, attempted to illuminate the events through then-recent revelations and declassified U.S. intelligence documents, republishing a text by British historian and military researcher John Costello. The starting point of the text is the same question that continues to intrigue historians and researchers:
Why were the United States so surprised?
An indicative reaction came from U.S. Secretary of the Navy Frank Knox upon receiving the first telegram:
“My God, it can’t be true, he must mean the Philippines.”
This was Knox’s reaction when, on December 7, 1941, he received the urgent telegram: AIR ATTACK ON PEARL HARBOR.
President Franklin Roosevelt had a similar reaction, interrupted in the middle of his meal by Knox’s call. What astonished American officials was not that Japan had launched the Pacific War, but that the attack occurred in Hawaii—5,000 miles east of the Philippines, where the strike was expected.
Aerial Photograph of a Japanese Aircraft during the Attack on Pearl Harbor
“Why such astonishment when Americans were almost certain that Japan would eventually attack them?”
Codes, Leaks, and Washington’s False Certainty
Historian Costello revealed that U.S. intelligence had long decrypted Japanese diplomatic communications (the “Purple” code) but not the Japanese naval military codes:
“…although they had been reading Japanese diplomatic messages encoded in the system known as ‘Purple,’ they had not managed to penetrate the complex military codes used to send messages to the navy and army. That penetration was achieved only a year after the Pearl Harbor attack.”
Thus, it is now evident that Washington relied excessively on these diplomatic messages, believing they alone would reveal when and where the Japanese attack would occur. However, “Purple” did not provide specific warnings, and U.S. intelligence was unaware that Hawaii was a major target in Japan’s war plans.
The “Key Message” Decrypted Years Later
The text emphasizes a secret Japanese message sent from Berlin to Tokyo, intercepted by the U.S. on December 12, 1941, but decrypted only in 1945.
“Only last April were a series of previously secret documents made public, containing a message so important that it forces us to reconsider our understanding of the events leading to the outbreak of the Pacific War […]”
TO VIMA reproduced the Japanese message, which revealed that the Germans had informed Tokyo of an internal British War Cabinet document:
“This afternoon I received from the German navy details of the British War Cabinet meeting held on August 15 concerning operations against Japan […] In the meantime, here are the main points:
- Although Japan aims to seize Singapore, Britain’s current situation will not allow its fleet to send reinforcements to the Far East, so it will have to defend the island with military and air forces.
- Japan will likely invade French Indochina or Siam as a first step, followed by the Dutch East Indies and Singapore […].
- Hong Kong will be abandoned, but resistance will continue as long as possible…”
The accuracy of this report was later confirmed by its striking similarity to the British memorandum of July 31, 1940, titled: “THE SITUATION IN THE FAR EAST IN CASE OF A JAPANESE ATTACK ON US”, which formed the basis of British War Cabinet discussions in early August. The memorandum presented a grim picture of Britain’s ability to defend its extensive holdings even with Dutch assistance, without American intervention.
Political Tensions in Tokyo Foretelling the Storm
This information exacerbated disagreements within the Japanese government between Prime Minister Konoe and the pro-Axis Foreign Minister Matsuoka.
Britain’s weakness in the Far East strengthened arguments for a southern attack, but the Imperial Navy feared direct conflict with the U.S. Ultimately, political uncertainty in 1941 led to Konoe’s fall and the rise of the militarists.
Warning Signs Misinterpreted
“Once the Japanese decided to attack, their intentions became clear in their signals […]. The most noticeable warning came from messages exchanged between Berlin and Tokyo. On November 27, the Foreign Minister in Tokyo informed Ambassador Oshima in Berlin that negotiations in Washington between Americans and Japanese ‘would break off in two or three days.’ On November 30, the ambassador received orders to notify Hitler that hostilities between Japan and the Anglo-Saxons would begin at any moment.”
Even as the signals multiplied in the days immediately before the attack, U.S. officials remained convinced that the threat lay in the Western Pacific:
“On the afternoon of December 6, Dorothy Etzgers, working in the Japanese section of U.S. Naval intelligence, intercepted a message about the signal lights that a Japanese agent would use in Honolulu to indicate the number of U.S. warships at Pearl Harbor. Etzgers immediately gave the message to officer Alwin Kramer. But he was swamped with diplomatic ‘Purple’ code messages and ignored the suspicious signal. ‘It can wait until Monday,’ he said.”
There were other indications that were also overlooked. On December 2, the Dutch in Java intercepted signals about Japanese plans in the Pacific and passed them to the U.S., while an American steamer traveling to San Francisco also intercepted signals from a Japanese fleet moving toward Hawaii.
The Fatal Certainties of Phillips and MacArthur
Costello also points to the overconfidence of two key commanders: British Admiral Phillips in Singapore and American General MacArthur in the Philippines. Both believed they could counter any Japanese move, but reality tragically proved them wrong.
MacArthur, despite warnings, did not order a preemptive strike on Japanese bases in Formosa:
“In Manila, MacArthur awoke to news that the U.S. fleet had been bombed. Within an hour, Washington had warned him not to be surprised if he were attacked soon. Yet, unbelievably, MacArthur did not use his greatest asset, his heavy bombers, to carry out a preemptive morning strike on Japanese air bases in Formosa.
If he had, his planes would have caught Japanese aircraft on the ground, grounded by the weather. Instead, by noon, no fighters were in the air to counter the Japanese air raid, which destroyed half of MacArthur’s planes on the ground.”
In Singapore, Admiral Phillips sailed without adequate air cover, despite receiving the discouraging message: “AIR SUPPORT IMPOSSIBLE.”
“A more experienced naval officer would have immediately realized that the mission was impossible. But for Phillips, retreat was completely foreign to Royal Navy tradition.
Forty-eight hours later, he and his two proud ships, Prince of Wales and Repulse, were at their watery grave in the South China Sea.”
