American Military History, Volume 1 by Richard W. Stewart

For the United States the opening years of the twentieth century were a time of transition and change. At home it was a period of social change, often designated the Progressive Era, when political leaders such as President Theodore Roosevelt undertook to solve the economic and social problems arising out of the rapid growth of large-scale industry in the late nineteenth century. Increasing public awareness of these problems as a result of the writings of the "Muckrakers" and social reformers provided popular support for efforts to solve them by legislative and administrative measures. In foreign affairs it was a period when the country had to begin adjusting its institutions and policies to the requirements of its new status as a world power with imperial responsibilities. In spite of a tendency after the end of the War with Spain to follow traditional patterns and go back to essentially isolationist policies, the nation's new responsibility for overseas possessions, its expanding commercial interests abroad, and the continued unrest in the Caribbean made a reversion to insularity increasingly unfeasible.

The changing conditions at home and abroad inevitably affected the nation's military establishment. During the decade and a half between the War with Spain and American involvement in World War I, both the Army and the Navy would undergo important reforms in organization and direction. Although the United States did not participate in any major conflict during these years, both services were frequently called upon to assist with administration of newly acquired possessions overseas. Both aided with protection of investments abroad threatened by native insurrections, revolutions, and other internal disturbances. And both contributed in other ways to upholding the vital interests of the nation in an era of greatly increased competition for commercial advantage and colonial empire. Much of the experience gained in the decades of the Indian Wars was used to great advantage in the essentially constabulary duties required to police an empire, but much needed to be done to modernize the military and prepare it for its new role in world affairs.