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Japan’s Motives for Bombing Pearl Harbor, 1941

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Editor’s Note: Jeffrey Hackler developed the following lesson for use in high school U.S. History courses. Upon completion of the lesson, students should have a better understanding of why Japan’s leaders ordered the attack on Pearl Harbor.

Recommended Course and Grade: United States History, 11th grade and up.
Instructional Objectives: Students will be able to: (1) Explain the predicament Japan faced in the Pacific during the first half of the twentiethth century leading up to December 1941. (2) Understand the Japanese leaders’ motives in attacking Pearl Harbor.

Most U.S. History textbooks offer students only a cursory explanation of Japan’s decision to attack Pearl Harbor. While there is no single correct or simple reason for the attack, this lesson should help students realize that Japan’s motivation for attacking Pearl Harbor was driven by its political self-interests, its scarcity of economic resources and perceived opportunity costs, and America’s embargo policy. It should also become apparent to students that long-term as well as short-term events soured relations between Japan and America.

Historical Background for the Teacher: In 1853, Commodore Perry ended Japan’s years of self-imposed isolation. Shortly thereafter, the Tokugawa Shogun agreed to a series of “unequal” treaties with the “great” nations of the West. After the Tokugawa collapsed, the Meiji leaders, starting in the 1870s, made it their number one priority to modernize the country as quickly as possible. They thought that if they could imitate the Western model politically, economically, militarily and socially, then the “great” nations would remove the “unequal” treaties and Japan could emerge as one of the “great” nations of the world. It was an ambitious goal, but it seemed possible. Japan had an abundance of labor, capital, and a small, literate population with the will to transform itself.

However, Japan had a problem. Because of its meager natural resources, the leaders realized that the country could not, on its own, catch up to the West in terms of its industrial output. To find more iron ore, coal, and—as the population started to increase— more foodstuffs, Japan looked at neighboring areas for raw materials. Japan entered into and won two wars against her neighbors, China in 1894–5 and Russia in 1904–5, in order to secure natural resources from the Korean peninsula and the Manchurian region, located in the northeastern region of China.

At the end of World War I, the goal of the Meiji leaders was attained when Japan was recognized as one of the “great” nations by the Treaty of Versailles. During the 1920s, Japan continued to industrialize and established peaceful economic and diplomatic ties with countries around the world in order to find more raw materials and markets for their finished goods. In particular, Japan developed strong ties with Manchuria and the U.S. In Manchuria, Japan found the necessary resources of grains, coal and iron ore; from the U.S., Japan imported petroleum, steel, scrap iron and other materials. All went well until the end of the decade.

Japan’s economic self-interest forced dramatic changes in her domestic and foreign policy during 1929–31 as it suffered the economic effects of the Great Depression, nervously watched the growth of Chinese nationalism, and was impressed by the rise of the military-led authoritarian governments of Germany and Italy. Facing a scarcity of resources, a growing population, and an economic depression at home, Japan assessed its comparative costs, decided that China and Russia were inferior to Japan’s might, and set out on a path of military conquest rather than peaceful trade and diplomatic negotiations with her neighbors. Japan first overran Manchuria and turned it into a Japanese puppet state by 1932. It attacked strategic regions and cities in China starting in 1937. The only Western reactions to Japan’s actions were to voice criticism and to issue harmless policy statements. In essence, the West and the U.S. were reluctant to take steps that carried any chance of initiating war with Japan. This was particularly prevalent in the U.S. where isolationist sentiment was strongly supported by many elements of the public.

In 1940, America did impose economic sanctions on Japan such as banning the export of iron ore, scrap iron and steel in the hopes that such a deprivation might stop Japan’s imperialistic advance into China and Indochina. It did not work. In July 1941, the U.S. ended all trade with Japan and froze all of Japan’s assets in the U.S. Great Britain, China and the Netherlands joined the U.S. in placing an embargo on oil exports to Japan. Japan was now deprived of several vital resources necessary for its economic survival.

At that moment, Japan had several choices. Option One was to stop and abandon its imperialistic conquests in Asia. Option Two was to maintain the “status quo” which would have ultimately forced Japan’s economy to grind to a halt. Both of these options would have caused Japan to “lose face.”

In order to replace embargoed resources and to establish its own economic sphere of influence (the Greater East Asia Co-prosperity Sphere) Japan pursued option three. Japan planned to gain control of parts of Southeast Asia, including the Malay Peninsula, Indonesia, and the Philippines, as well as many Pacific Islands. In order to make the last option work for as long a period of time as possible, Japanese leaders wanted to eliminate or to at least minimize the presence of the strong U.S. Navy in the Pacific, one which had the potential to disrupt the shipping lanes in the East China Sea and thereby thwart Japan’s plans for a Greater East Asia Co-Prosperity Sphere. This was Japan’s hope when it launched the attack on the U.S. Navy stationed at Pearl Harbor on December 7, 1941.





Scarcity – not enough of an item or resources to fill a desire.

Opportunity Costs – the next best alternative.

Comparative Costs – compare two similar goods and choose the better value.

Sphere of Influence – a portion of one country controlled and influenced by a foreign country primarily for economic reasons.

Open Door Policy – The U.S. wished to preserve equal economic opportunity in all of the spheres of influence in China starting in 1900.


Time: One class period (60 minutes). The teacher should determine ahead of time how to use the class period effectively. If it is a long class (60+ minutes), be sure to leave 10 minutes at the end of class for the evaluative writing assignment (Step F). If it is a shorter class period, assign the evaluation writing assignment for homework.

The key to this lesson: Be sure to leave plenty of class time for discussion and debates as students test out their ideas. The questions in Step E also produce a lot of discussion. The “ah-ha” moment comes when the students challenge each other’s views about how wars begin.

The Previous Night‘s Homework Assignment: Have the students read their U.S. History textbook and locate all references which mention the Japan-U.S. friction between 1900–41 or 1931–41. The information might be sketchy and brief, but the students should be prepared to offer at least one explanation as to why Japan attacked Pearl Harbor. Also, students should look at their textbook’s World War II map of the Pacific War which shows not only the extent of Japan’s territorial acquisitions but also America’s leapfrogging advances on Japan.


Step A (spend about 5–10 minutes)

The teacher should begin class by asking:

What were the political reason(s) the textbook gave for Japan’s attack on Pearl Harbor?—write the cause(s) on the board.

What were the economic reason(s) the textbook gave for Japan’s attack on Pearl Harbor?—write the causes on the board.

Are the students satisfied with the answers on the blackboard? What other information would they want to know?

Step B (15–20 minutes)

Arrange the students into groups of three or four.

Give one copy of Handout #1 to each group. Students in each group must fill in all three columns for the 20 items and must be prepared to defend their choices. (Let the students know that some items have multiple answers.) Step C Now give every student Handout #1 so each student can copy down the class’s (not the group’s) answers.

Step C

Now give every student Handout #1 so each student can copy down the class’s (not the group’s) answers.

Step D

Let one group after another lead the class in discussing their conclusions. Rotate the groups so that all share leadership responsibilities. (approximately 20 minutes)

The Teacher’s Role in Step D is to

  1. clarify points of disagreement;
  2. start a discussion over some of the groups’ answers and
  3. remind the students that they are simulating the Japanese leaders’ decision-making process.

Step E (remainder of period)

When the students have completed discussing the handout, the teacher should ask:

  1.  What does Handout #1 reveal about the Japanese leaders’ decision-making process?
  2. What were Japan’s “opportunity costs” in late 1941?
  3. What were the three options open to Japan after the U.S. placed an embargo on all Japanese goods and froze all Japan’s credits?
  4. Why did Japan choose to attack Pearl Harbor first and not the Philippines or Indochina?
  5. How could the U.S. act so justifiably outraged by the Pearl Harbor attack? Did the U.S.’s actions force Japan to attack Pearl Harbor?
  6. At what point was the attack inevitable?
  7. What does Handout #1 tell us about any country’s decisions to go to war?

Step F

Student evaluation (short essay assignment in class or homework)

Teacher may assign some of the unanswered questions in Step E or ask the following questions:

  1.  If you were a Japanese leader in 1941, what would be your feelings after looking at all the evidence? Can you think of another option other than bombing Pearl Harbor?
  2. Japanese Admiral Yamamoto said after the Pearl Harbor attack, “I fear we woke a sleeping giant.” What did he mean? How does this reflect upon the Japanese decision-making process? What factors did the Japanese not take fully into account? Would those factors have swayed the Japanese leaders to not launch the attack on Pearl Harbor?
  3. To what degree do you think American leaders were “surprised” by Japan’s bombing of Pearl Harbor on December 7, 1941? Could American leaders have used other means in 1940 and 1941 to persuade the Japanese to stop their imperialistic ways?


The teacher may want to discuss Step A at the end of a class and give Handout #1 as homework. That would save time in class, since steps B and C could be skipped thereby allowing more discussion time in class for steps D and E.

The teacher may want to cut the number of items in Handout #1 from 20 to 14; any less, and the lesson is too watered down. Simplifying means the students would spend less time on Steps B and D but still allow the students plenty of time for discussion.

The teacher could also assign one of the questions from E as a written homework assignment and save the questions from Step F for the next test.

The following resources provide additional background on the Japanese decision to bomb Pearl Harbor.


Bergamini, David. Japan’s Imperial Conspiracy. New York: William Morrow & Co., Inc., 1971.

Bix, Herbert P. Hirohito and the Making of Modern Japan. New York: Harper Collins Publishers, Inc., 2000.

Feis, Herbert. The Road to Pearl Harbor: The Coming of the War between the United States and Japan. New York: Atheneum Press, 1962.

Goldstein, Donald M., and Katherine V. Dillon (eds.). The Pearl Harbor Papers: Inside the Japanese Plans. Dulles, Virginia: Brassey’s, Inc., 1999.

Ike, Nobutaka (ed.). Japan’s Decision for War: Records of the 1941 Policy Conferences. Stanford: Stanford University Press, 1967.

Morley, James William (ed.), David A. Titus (trans.). The Final Confrontation: Japan’s Negotiations with the United States, 1941. New York: Columbia University Press, 1994.

Neu, Charles E. Troubled Encounter: The United States and Japan. New York: John Wiley and Sons, Inc., 1975.

Neuman, William L. America Encounters Japan: From Perry to MacArthur. Baltimore: Johns Hopkins Press, 1963.

Prange, Gordon William, Donald M. Goldstein, Katherine V. Dillon. At Dawn We Slept: The Untold Story of Pearl Harbor. New York: Viking Penguin, 1982.

Toland, John. The Rising Sun: The Decline and Fall of the Japanese Empire, 1936–1945. New York: Random House, Inc., 1970.

Van Alstyne, Richard W. The United States and East Asia. New York: W. W. Norton and Co., Inc., 1973.