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The Japanese attack on Pearl Harbor in Hawaii on December 7, 1941, thrust the United States into World War II. The surprise aerial attack killed over 2,400 Americans and sank or damaged numerous battleships and aircraft.

If you’re short on time, here’s a quick answer to the question of why Japan launched this attack: Japan needed to limit American naval power in order to achieve its goal of creating a self-sufficient empire including resource-rich European colonies in Southeast Asia.

In this comprehensive article, we will analyze the strategic reasoning behind Japan’s attack on Hawaii. We will cover Japan’s larger expansionist goals, the threat the U.S. Pacific fleet posed to those goals, how crippling the fleet would open opportunities for Japan, and more.

By the end, you will have a detailed understanding of the strategic considerations that made Pearl Harbor the target.

Japan’s Need for Natural Resources Drove Expansion Efforts

Buildup of Military Power in 1920s-1930s

In the 1920s and 1930s, Japan began a major buildup of its military power. Having very few natural resources domestically, Japan looked to obtain access to raw materials like oil, rubber, and iron ore.

This drove Japan’s expansionist foreign policy, which sought to obtain control and access to the natural resources of neighboring countries and territories.

Specifically, Japan greatly expanded its navy in this period, seeing control of the seas and ability to project power abroad as key to achieving its goals. The navy grew from the 5th largest in the world in 1920 to the 3rd largest by 1941.

The army also grew considerably, developing advanced weaponry and equipment.

Lack of Domestic Natural Resources

A major motivation behind Japan’s military buildup and expansionism was its lack of natural resources domestically. Japan has very little oil, rubber, iron ore, coal, and other vital resources required by a modern industrial economy and military.

For example, Japan produced only 7% of the oil it consumed as of 1941. It was completely dependent on imports for sources like rubber and iron ore. This lack of natural resources was a strategic vulnerability for Japan.

Securing control of the oil, rubber, metals and other resources of neighboring nations became a key driver of Japan’s increasingly militant foreign policy through the 1930s. For example, Japan’s eye was focused on the petroleum resources of Indonesia and Borneo.

Western Colonies as Targets

A related factor was the presence of rich natural resource bases in the European (and American) colonies close to Japan, specifically in Southeast Asia and the Pacific. Areas like French Indochina, the Dutch East Indies, and British Malaya (today Vietnam/Laos, Indonesia, and Malaysia) had abundant natural resources but were controlled by western colonial powers.

Japan saw these European colonies as prime targets for expansion, both to gain access to critical resources and also to strike blows against the western powers. By 1941, Japan had military plans ready for conquering areas like Malaya, Java, and Borneo by force with the goal of exploiting their resources to fuel the Japanese war machine.

The Increased isolationism and sanctions imposed by western powers in the 1930s (especially oil exports) made Japan increasingly desperate to secure its own oil and resources bases, by force if necessary.

This was a major factor behind imperial Japan’s decision to attack and attempt to control European (and American) territories in 1941, bringing the USA into WWII.

U.S. Pacific Fleet Blocked Japan’s Regional Goals

In the early 20th century, Japan sought to establish itself as the dominant power in Asia. However, the sizable U.S. naval presence in the Pacific, centered around the Pacific Fleet based in Hawaii, stood in the way of Japan’s ambitions.

The attack on Pearl Harbor was intended to neutralize the U.S. Pacific Fleet so that Japan would have a free hand in pursuing its goals in Southeast Asia and the Western Pacific.

The Pacific Fleet Deterred Japanese Expansionism

By 1941, the Pacific Fleet consisted of nine battleships, three aircraft carriers, and attendant cruisers, destroyers, and submarines based at Pearl Harbor. This powerful fleet would have contested any Japanese attempts to seize European colonies in Southeast Asia or establish a Japanese sphere of influence.

Japanese military leaders decided the fleet had to be knocked out before they could embark on their plans without American interference.

The Pearl Harbor Attack Sought to Paralyze the Fleet

On December 7, 1941, Japan launched a surprise air attack on the U.S. Pacific Fleet at Pearl Harbor. Wave after wave of Japanese bomber and fighter planes struck the unprepared fleet and airfields around Oahu.

By the end of the attack, Japan had sank or damaged eight battleships, three cruisers, three destroyers and 188 aircraft. The raid was a huge tactical success, crippling the Pacific Fleet’s offensive capability for over a year.

Japan hoped that with the U.S. fleet out of action, it could pursue its expansionist plans across the Western Pacific and Southeast Asia without American intervention. However, the attack galvanized the American public’s support for entering World War II and ultimately set the state for Japan’s defeat.

Attacking Hawaii Would Allow Japan to Expand Empire

Temporarily Neutralize U.S. Naval Power

Japan’s attack on Pearl Harbor was intended to temporarily knock out the U.S. Pacific Fleet so that Japan could pursue its expansionist goals in Southeast Asia without interference (1). By crippling the fleet, Japan hoped to neutralize America’s ability to respond militarily at least for several months.

This would buy Japan valuable time to conquer territories and strengthen its defenses before the inevitable U.S. counterattack.

Admiral Isoroku Yamamoto, the architect of the raid on Pearl Harbor, knew that Japan could not win a protracted war against the industrial might of the United States. So he devised a bold plan to deal a severe initial blow that would shift the balance of power in Japan’s favor long enough to establish a defensible perimeter encompassing the Dutch East Indies and other resource-rich territories in the region (2).

Provide Window for Conquest in Southeast Asia

Without the threat of U.S. intervention, Japan intended to swiftly conquer areas of Southeast Asia, including present-day Indonesia, Malaysia, Singapore, and the Philippines. The natural resources gained, especially oil, rubber and metals, would fuel Japan’s war machine and strengthen its economy (3).

This blitzkrieg-style campaign of lightning conquests depended on keeping the U.S. sidelined in the short term. Japan had neither the strength nor sustainability to win a fight on two fronts against the Americans and the Allied powers in Southeast Asia at the same time.

Catching the U.S. Pacific Fleet unawares at Pearl Harbor was thus an essential precursor to Japan’s wider warring ambitions.

Chance to Strengthen Defenses

As well as subjugating territory for imperial expansion and resource extraction, Japan envisioned using the time afforded by disabling the U.S. Pacific Fleet to fortify its new island empire, making it costlier and harder for the U.S. to retake (4).

Yamamoto hoped that by increasing the defensive perimeter and raising the casualty toll on American forces needed to breach it, the Japanese military leadership could force the U.S. to eventually negotiate a peace rather than pay the heavy price of invasion.

This was a major miscalculation, as Yamamoto had earlier warned Japanese officials that Japan going to war with the U.S. would be like “fighting a war against steel.” But the Pearl Harbor attack was Japan’s attempt to improve those impossible odds.

In the end, the material advantages of American industry and technology could not be neutralized even by the most daring tactical maneuvers. But Japan’s longshot bid to change the course of the war was a strategic gambit borne of desperation and nationalistic militarism.


In the early 1940s, Japan’s expansionist goals in Southeast Asia were threatened by the increasing U.S. economic and military presence in the region. By launching a surprise attack to cripple the United States Pacific Fleet at Pearl Harbor, Japan removed the most direct obstacle blocking its regional ambitions.

This gave Japan an opportunity to invade European colonies unimpeded while defenses around the home islands were bolstered. The Pearl Harbor attack can rightly be seen as the opening strategic move enabling Japan’s attempted Pacific empire-building, even if its long-term consequences proved catastrophic.

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