In the final decade of the nineteenth century, the United States transformed itself into an imperial power. Presidents McKinley and Roosevelt carried out the strategy outlined by Captain Alfred Thayer Mahan to enlarge the navy, construct a canal linking the Atlantic and Pacific Oceans, and acquire coaling stations and bases in the Pacific to service the fleet. U.S. officials disregarded the nationalistic aspirations of freedom fighters such as José Martí in Cuba and Emilio Aguinaldo in the Philippines in favor of the imperial spoils gained from winning the War of 1898. The United States justified intervention on moral grounds predicated on racist beliefs, much as it had in conquering the Indians during westward expansion. As a fit and manly nation, the United States had the responsibility to uplift inferior peoples to “civilized” standards and make them capable of self-government. This justification quickly wore thin. To crush the rebellion in the Philippines, the military engaged in atrocities that called into question the honor and virtue of the United States. Once it achieved victory in the Philippines, the nation concentrated its efforts on maintaining territories primarily for commercial purposes. Within the few short years from 1898 to 1904, this commercial empire had fallen into place.

The Progressive Era presidents, Roosevelt and Wilson, created and sustained a U.S. empire. They disagreed significantly in approach—Roosevelt favoring force, Wilson preferring negotiations—but in practice they shared a willingness to use military power to protect national interests. These two presidents helped construct the modern American state, an expanded federal government that officially sanctioned cooperation with responsible corporate leaders. This relationship reached its peak during World War I. In mobilizing the home front, the Wilson administration blurred the line between public and private business by expanding the reach of government over the economy and curtailing personal liberty.

In 1917, because of its heavy reliance on trade with foreign countries, especially in Europe, the United States confronted its first major international crisis of the twentieth century. Wilson reluctantly led the country into war to guarantee a world order in which reasonable nations attempted to resolve controversies through negotiation, not violence. The failure of the United States to join the League of Nations, for which the president was largely responsible, shattered that idealistic dream.

The United States retreated from joining an international body offering collective security, but it did not isolate itself from participation in the world. The country emerged from the war in excellent financial shape; it had become the leading foreign creditor, and its industrial capacity had greatly expanded. Tending its commercial empire in the Caribbean and Central America, the United States probed for new markets in Asia and the Middle East. It would take another two decades for policymakers to realize that the country’s refusal to support a strong collective response to expansionist aggression posed serious dangers for U.S. commerce and values.