The confrontation of the American reform tradition with the world conflicts in which the United States has been involved is a major theme in modern American history. With regard to the First World War, two questions have attracted particular attention. The first is the part played by the war in the decline of the progressive movement. The second is whether a commitment to domestic reform produced a particular approach to foreign affairs, and if so what the nature of this approach may have been. This latter issue has generated a lively historiographical debate. On the former, however, there has been general agreement that the war weakened the forces of reform in America. This has been conceded even by those who wish to stress the extent to which the progressive impulse persisted through the war and into the 1920s.

There has been less agreement, however, about the nature of the connection between war and the decline of progressivism. The suggestion is sometimes made that war always puts an end to reform. This generalization does not bear scrutiny. Even within the history of the United States, Radical Republicanism reached its apogee shortly after the Civil War, while the Progressive Era itself followed the Spanish-American War. From a wider perspective, there are many more examples of a tendency for war to promote reform or revolution. Unsuccessful war certainly endangers regimes, as the First World War demonstrated in Russia, Austria-Hungary, Germany, and Turkey. Even when unaccompanied by defeat, the experience of war can help to stimulate a desire for radical change, as it did in Britain in 1945.