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STEVE EMBER:The surprise attack on America's large naval base in Hawaii was a great military success for Japan. However, the attack on Pearl Harbor had more than a military meaning.

The attack would force Americans to enter World War Two. More importantly, it would also make them better recognize their position as one of the most powerful nations in the world.

In future weeks, we will discuss the military and political events of World War Two. But today, we look back at the years before the United States entered that war.

The period between the end of World War One and the attack on Pearl Harbor lasted only twenty-three years, from nineteen eighteen to nineteen forty-one. But those years were filled with important changes in American politics, culture and traditions.

We start our review of these years with politics.

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In nineteen twenty, Americans elected Republican Warren Harding to the presidency. The voters were tired of the progressive policies of Democratic president Woodrow Wilson. They were especially tired of Wilson's desire for the United States to play an active role in the new League of Nations.

Harding was a conservative Republican. And so were the two presidents who followed him, Calvin Coolidge and Herbert Hoover.

All three of these presidents generally followed conservative economic policies. And they did not take an active part in world affairs.