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On December 7th, 1941, the Japanese surprise attack against Pearl Harbor, in Hawaii, marked the onset of a gigantic military clash between Japan and the United States in the Pacific. It was to last a little less than four years, leading to the unconditional capitulation of Japan.

In the United States, Pearl Harbor was quickly presented as a premeditated, treacherous attack against an innocent nation, Franklin Roosevelt calling December 7th, “the day of infamy.” Sixty years later, the terrorist attacks of September 11th, 2001, were at once perceived as “a new Pearl Harbor”. The comparison is far fetched and does not withstand the test of an in-depth analysis of the military and geo-strategic context surrounding the Japanese attack against Pearl Harbor.

For one thing, Pearl Harbor was a military target. On November 10th, 1941, the Japanese military establishment had agreed upon a specific plan of action. The Japanese plan called for a quick and massive blow against American naval power in the Pacific, a carrier-based air attack on Pearl Harbor aimed at destroying the United States’ Pacific fleet. On December 7th, the Japanese attacked successfully. The Americans were caught by surprise.

Japan’s losses were insignificant; sixty-four dead, twenty-nine planes and four submarines. However, success was far from complete, the Japanese failing to destroy port infrastructures as well as oil and ammunitions depots and repair facilities.

On the American side, the casualties were much heavier; nearly two hundred aircraft destroyed on the ground, two battle cruisers irrecoverably lost, the Oklahoma and the Arizona, and nearly 2,500 sailors killed. But the other battleships, even those heavily damaged, were all reparable. More importantly, the American large aircraft carriers were not at Pearl Harbor. And the Japanese did not attempt to locate them in the high seas. The continued survival of America’s Pacific Fleet aircraft carriers, Lexington, Saratoga, and Enterprise, together with Yorktown, which was soon recalled from the Atlantic, would remain a constant source of concern for the Japanese in the months to come.

In any case, the American Pacific fleet was not annihilated on December 7th.

In the following months, until the decisive battle of Midway, which took place in the early days of June 1942, the Japanese swept through Southeast Asia, unopposed. The lack of significant American response had a great deal to do with Germany’s declaration of war against the United States, just a few days after Pearl Harbor. Franklin Roosevelt had always made it clear Germany would become the primary target the moment the United States entered the war alongside Great Britain. Stopping the Germans, who were fast approaching the outskirts of Moscow, became paramount.

Japan’s apparent success at Pearl Harbor gave it only a brief window of opportunity: five months. No one can deny that the attack was well conceived and completely caught the Americans by surprise; yet it was not a decisive victory.

Of more interest to the historian are the following questions: why did the Japanese attack Pearl Harbor in the first place? What set of circumstances triggered the attack? Did Japan seek to take advantage of the war in Europe and plan an unjustified, treacherous attack against the United States, or was it simply cornered into aggressive action by decisions made in Washington?

A thorough analysis of the chronology leading to the attack and a look at the evolving Americano-Japanese relations until 1941 should help us answer those questions.

Since creating a modern army and navy in the second half of the 19th century, Japan had sought to become a major power in the Pacific by building an empire, thus gaining access to the natural resources it lacked, coal, iron, and oil. From the start, its main long-term goal was to take advantage of China’s political instability.

In the 1930s, the rise to power of the military establishment in Tokyo gave a new impetus to aggressive expansionism, which translated, first in the invasion and occupation of the northern Chinese province of Manchuria, then in an all-out war against China in 1937.

Japan’s four-point strategy was laid out in two documents released in 1936, The Criteria for National Policy and The Foreign Policy of the Empire. First point, the economic development of Manchuria, which had many of the resources Japan needed so badly, and which presented the advantage of giving the Japanese a firmer foothold on the Asian continent for further advances; second, the gradual invasion and occupation of China’s other Northern provinces, backed by the Japanese Imperial Army and known as the Northern Strategy: it involved securing access to coal, iron and oil in northern China, Mongolia and Siberia; third, in conjunction with the second point, preparations for a possible conflict with the Soviet Union, which looked on Japan’s policy of aggression in northern China with mounting concerns. The fourth point, favored by the Japanese Imperial Navy had to do with gaining control of Southeast Asia and its resources (the Southern Strategy). To achieve this last objective, the Navy called for a major naval construction program.

If Japan’s military establishment kept on debating the choice of a strategy, it also

had to be mindful of the foreign policy of the United States, which was committed to creating and protecting new markets in the Middle Kingdom (the “Open Door Policy”), in other words promoting a stronger China. The rise of isolationist sentiments in the U.S., throughout the 1920s and 1930s, which climaxed with the passing of a series of Neutrality Acts in 1937, did nothing to reassure Tokyo. Indeed, as another war loomed in Europe, the Roosevelt administration remained committed to circumventing the staunch isolationism of both Congress and public opinion, thus helping Western European democracies. In 1939, the U.S. president signed into law a new Neutrality Act, which permitted American companies to supply arms to France and Great Britain on the condition they paid in cash and transported the goods on their own ships. This measure was followed up, in 1941, with the far more sweeping Lend-Lease Act, that is the transfer of war materials in exchange for theoretical deferred payment, which included China and the Soviet Union.

Therefore, the attitude of the United States remained a constant source of concern for the Japanese and influenced the making of Japan’s strategic policy in Asia after 1939, particularly as the Navy managed to impose its Southern Strategy. As it turned out, following repeated border disputes with the Soviet Union, which culminated with Japan’s crushing defeat at the battle of Khalkhin Gol, the Northern Strategy had lost all appeal and the Japanese had no choice but to reconsider their plans.

Sustaining a war of expansion against China and potentially against the major colonial powers established in Southeast Asia required the stockpiling of raw materials such as oil, scrap iron, iron ore and coal. While the conquest of China was to provide Japan with enough coal and iron-ore deposits, most of the country’s scrap metal, essential for naval construction, was imported from the United States. Also problematic was the question of oil: 90% of all Japanese aviation fuel and oil came from America.

By 1936, the Imperial Japanese Navy was importing 1.2 million tons of oil per year and would soon have 3.5 million tons stockpiled, but it was already burning 800,000 tons per year. And this was before the war with China escalated into a full-scale invasion. When the United States began restricting aviation fuel after 1939, the shortages faced by the Japanese military became even more acute. Stockpiling continued and, by the beginning of December 1940, Japan had 6.5 million tons of oil reserves for all uses. But that proved insufficient. The Japanese thus faced a dilemma: if America ended up cutting off all its oil supplies, Japan would have no choice but to seize the massive oil reserves in the Dutch East Indies and British North Borneo.

Three key events must now be considered to understand the chain of events leading to the December 7th attack: first, the German invasion of the Soviet Union, Operation Barbarossa, on June 21st, 1941; second, the decision by Japan, on July 2nd, to occupy the Southern part of French Indochina.; Third, the decision by the Americans, at the end of July, to freeze all Japanese assets in the United Stated and put [into effect] an embargo on all commodities, thus denying Japan 80% of its oil imports.

Throughout 1940 and 1941, Japan did not merely observe the evolution of the conflict in Europe. The swift collapse of France offered new opportunities. The Vichy regime was incapable of defending France’s far east colonies. It promptly agreed to concede rights of military transit and stationing in northern Indochina to the Japanese. From that new vantage point, Japan could strike easily at British Malaya, Burma, the Philippines, and the resource-rich Dutch East Indies. Washington saw Japan’s agreement with Vichy as yet another sign of mounting Japanese aggression, a threat to its vital interests in the Pacific region. To make matters worse, Japan soon struck an alliance with Germany and Italy, the Tripartite Pact, which stipulated that the signatories were “to assist each other in the European war or in the Sino-Japanese conflict,” should they be attacked.

On July 2, 1941, an imperial conference summoned by the Japanese Prime Minister, Prince Konoye, adopted a document entitled “Outline of the Empire’s National Policies in View of the Changing Situation.” It clearly acknowledged that a further move to Indochina would entail “risking war with Britain and the United States,” even though the possibility of a conflict was deemed remote.

In that same month of July, Japan’s decision to strengthen its positions in Indochina by occupying the French colony in its entirety must be analyzed in the light of its ongoing war with China. A statement released on August 1 by the Japanese Board of Information, emphasized the need to cut off the Chinese nationalists “from supply routes across the Indo-China-Yunnan border.”

In agreement with the Dutch government-in-exile and the British, the Roosevelt administration swiftly decided on a response. On July 26th, a full embargo on all commodities was implemented against Japan. Roosevelt signed an executive order “freezing Japanese assets in the United States.” The measure brought “all financial and import and export trade, transactions in which Japanese interests are involved under the control of the government,” thus preventing the Japanese from buying oil and other key resources.

Why such a forceful response?

First, the Americans were now convinced Japan was acting with the support of Nazi Germany. The two dictatorships were naturally helping each other. The tendency to believe a common ideology automatically translates into a common military strategy was to prevail again in the early days of the Cold War paving the way for the U.S. policy of containment against the spread of Communism. Yet, on June 21, through its ambassador in Washington, the Japanese government had re-affirmed that the purpose of the Tripartite Pact “was, and is, defensive and is designed to contribute to the prevention of an unprovoked extension of the European war.” On July 8, the Japanese reassured Washington they had no intention of “joining the hostilities against the Soviet Union.”

Secondly, the Roosevelt administration suffered from a lack of communication[s] between its various services. If a memorandum dated July 19 on the “Effect of Further Restrictions on Exports [to Japan],” recommending “that trade with Japan not be embargoed at this time,” was quickly dismissed by Roosevelt, the embargo was to be gradual, not total. However, Dean Acheson, assistant Secretary of State, chose to keep that crucial piece of information to himself, hoping a more drastic measure would force Japan to reconsider its aggressive moves. A full embargo it was to be, after all.

Third, instead of considering an acceptable agreement with Japan, the United States chose to put pressure on Japan by increasing its demands for a full withdrawal from China and Indochina. Only then would they consider a partial lifting of the embargo.

By the end of the summer of 1941, the Japanese military had, therefore, a major dilemma on its hands. Without the American oil, it could not sustain its war against China and pursue its expansionism toward the creation of its new order in Greater East Asia.

The Japanese underestimated the American reaction. The United States overestimated the Japanese threat. Few in either country wanted a full-scale war.

The urgency imposed by the American full embargo united the Japanese military, at last. From that point on, diplomatic talks were nothing more than a stalling tactic, allowing the Japanese Navy to set up its plan of attack. War preparations were to be completed by the end of October. If, by that time, Japan’s demands were not met by the United States and Britain, namely a free hand in China, Japan would attack.

The Japanese were not ready to give up their imperial ambitions. Their only remaining option was to seize the natural resources they needed and strike further south at British Malaya and the Dutch East Indies, more than likely triggering a further reaction from the U.S. To prevent such a response, the Japanese then made the fateful decision to attack and destroy the American Pacific fleet at Pearl Harbor. With their fleet severely crippled, the Americans would not be able to interfere with Japan’s plans. Japan would then have plenty of time to dig in defensively and consolidate its gains.

By imposing a full embargo, there is no doubt the Roosevelt administration forced the Japanese into action in December 1941. But was there an alternative? In any case, meeting the U.S. demands and withdrawing from China and the Tripartite Pact was not something could or would consider. In the end, Japan proved no match for the United States. The tide turned against the Japanese within six months, just as Admiral Yamamoto had predicted.


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