The Late 1700's: Warnings Against Involvement
The United States had just emerged from the War of Independence, and was too busy creating a government to meddle in the affairs of other nations The new nation quickly created ambassadorships to major European nations. But the early mood of the nation was decidedly isolationist. In his farewell address, George Washington said, "It is our true policy to steer clear of permanent alliances with any portion of the foreign world," and that "The great rule of conduct for us, in regard to foreign nations, is, in extending our commercial relations, to have with them as little political connection as possible." During the Napoleonic Wars that divided Europe (1793 - 1815), the United States remained neutral, continuing to trade with all sides.

Read Washington's Farewell Address

1823: The Monroe Doctrine
On December 2, 1823, during his annual message to Congress, President James Monroe stated what came to be known as the "Monroe Doctrine." The doctrine sought to isolate the entire Western Hemisphere, saying, "The American continents, by the free and independent condition which they have assumed and maintain, are henceforth not to be considered as subjects for future colonization by any European powers." While he warned European nations to stay out of North and South America, Monroe promised European leaders "not to interfere in the internal concerns of any of its powers." Monroe drafted the doctrine to keep the Western Hemisphere out of the fighting that had been plaguing the European continent for decades.

Read the Monroe Doctrine

1904: The Roosevelt Corollary
President Theodore Roosevelt issued an addition, or corollary, to the Monroe Doctrine in 1904. Essentially, Roosevelt positioned the United States as the policeman of the Western Hemisphere, saying that, "In the Western Hemisphere the adherence of the United States to the Monroe Doctrine may force the United States, however reluctantly, in flagrant cases of such wrongdoing or impotence, to the exercise of an international police power." The corollary was implemented when Roosevelt authorized U.S. military intervention to suppress revolutions in Latin America which might have threatened the stability of the region. Critical historians have argued the interventions were designed to protect U.S. business and trade interests in these countries.

Read the Roosevelt Corollary

Woodrow Wilson and Engagement
On February 3, 1917, President Woodrow Wilson asked Congress to delcare war on Germany. Although Wilson had run on a campaign promise to keep the United States out of World War I, he was forced to reverse his position after German U-boats sunk the Lusitania, killing 120 Americans. In his message to Congress, Wilson painted the war as the U.S.'s moral duty. And he promised to create an international organization that would end all wars forever. After victory in the war, Wilson helped establish the League of Nations, the forerunner to the United Nations. He also advocated no occupation of the defeated nations and policies to ensure free trade among all nations. Ultimately, some conservative Senators and world leaders undermined Wilson's efforts: Germany was hit with harsh reparations and the U.S. never actually joined the League of Nations.

Read the Treaty of Versailles (ended WWI and created the League of Nations)

1920: "Return to Normalcy"
In 1920, Warren Harding, arguably the most mediocre President in U.S. history, easily won the 1920 election running on the slogan "A return to normalcy." After Woodrow Wilson's vision for a new world order, Americans were anxious to retreat from the world stage. When the Depression hit, Americans were even less interested in being involved in European affairs. In the mid-1930's, a Senate panel concluded that the U.S.'s involvement in World War I had been a mistake. As Hitler, Franco, and Mussellini rose to power in Europe, American public opinion called for a hands-off approach to the mounting European tensions.

Pearl Harbor: Forced Engagement
As war raged in Europe, the U.S. maintained its neutrality. Americans were still recovering from more than 116,000 military casualties in World War I. On December 7th, 1941, the war could be ignored no longer. After the Japanese attack on Pearl Harbor, President Franklin D. Roosevelt asked Congress to declare war. The Pearl Harbor attack marked the end of U.S. isolationism. After victory in the war, the U.S.-brokered Marshall Plan was instituted to rebuild Europe. It essentially ensured a U.S. military and economic presence overseas for decades to come.

Read the speech that launched the Marshall Plan

The Truman Doctrine
On March 12, 1947, President Harry S Truman asked Congress to help Greece and Turkey, both of which were struggling to subjugate communist uprisings. In the speech, Truman effectively overturned the U.S.'s tradition of isolationism, saying that "It must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures." In the new world order that left the globe with only two superpowers, Truman said "The free peoples of the world look to us for support in maintaining their freedoms. If we falter in our leadership, we may endanger the peace of the world -- and we shall surely endanger the welfare of our own nation." After nearly two centuries of staying out of world affairs, the U.S. ventured out to protect democracies that might be threatened by the spread of communism. The Truman Doctrine was used to explain U.S. military campaigns in Vietnam and Korea.

Read the Truman Doctrine

The Current Debate
The decision of the U.S. to intervene in an international dispute inevitably provokes a two-century-old debate: Should the U.S. enter disputes involving other nations? With the end of the Cold War, presidents could no longer use the containment of Communism as a justification. In the post-Cold War era, two schools of thought emerged. Isolationists, like Patrick Buchanan, argue that U.S. should not use its money or its soldiers to settle other nations' disputes. Others say the U.S. has a moral responsibility, as the lone superpower, to weigh in when freedom and human rights are attacked. In the wake of the September 11th attacks, the world has changed once again. The question remains: should the U.S. be more isolationist or more engaged in world affairs?

Click here for a discussion of this issue on "Special Coverage."