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Pacific 1939-1945: Pearl Harbor

Why was the USA so unprepared for the attack on Pearl Harbor in 1941?

A statement by US President Truman on the outcome of the enquiry into Pearl Harbor, August 1945

Catalogue ref: ADM 199/1363

President Truman on the outcome of the enquiry into Pearl Harbor, August 1945; ADM 199/1363

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What is this source?

This source is a press statement made by US President Truman in August 1945. When he mentions the President in his statement he is referring to the previous President, Franklin D Roosevelt.


Truman became President in April 1945 after the death of President Roosevelt.

What’s the background to this source?

WWW2 broke out in Europe in 1939. The USA was neutral in the early stages of the war although it was clear that US President Roosevelt was no friend of Nazi Germany or its ally Japan. In Japan, hard line military commanders had become increasingly powerful during the 1930s. Japan had built up an empire in Asia and these leaders wanted Japan to become Asia’s leading power. They knew that the USA would stand in their way and that war with America would happen some time. They decided to try and knock out the US fleet in the Pacific. The plan was to buy time to build up their resources in the Pacific so that Japan would be ready to take on the USA once it recovered from the attack at Pearl Harbor.


There were large numbers of Japanese settlers in Hawaii in 1941. Some were Japanese immigrants but far more were descendants of immigrants and were therefore American citizens. Even so, around 120000 Japanese Americans were interned in camps during the war.

It’s worth knowing that...

As soon as war broke out in 1939 President Roosevelt was very concerned. He feared that if Nazi Germany won the war in Europe it would be a threat to the security of the USA. However, most Americans were totally opposed to involvement in the war.


Roosevelt sent vast amounts of vital war equipment and medical supplies to Britain and her allies in what was called the Lend Lease scheme. There is not much doubt that Roosevelt and his chief advisers felt war was inevitable with both Japan and Germany.

How will you use this source?

  1. According to this source, who or what was to blame for Pearl Harbor?
  2. In what ways does this view contradict or support other sources in this investigation?
  3. Could any parts of this source be used as evidence in your report on the key question?

Use this table to help plan your report.