One of the central questions of the history of the First World War is whether autocracies or democracies were better at waging war. This chapter surveys the way in which different political structures responded to the challenge of war. The global character of military conflict was limited, except with respect to Japan and to the United States at a late stage, both with great consequences. When the First World War broke out, five European states were at the centre of events: Russia, Germany, Austria-Hungary, France and the United Kingdom. The first non-European state to enter the war when it had barely begun was, paradoxically, Japan. Woodrow Wilson engaged the United States in the war for the freedom of the seas and the survival of democracy in the world. Georges Clemenceau's government is considered as the first war government. It was the most representative regimes which won the war and that everywhere in Europe, after the war, democracy was predominant.