Which Allied Power ended up having to enforce the Treaty of Versailles by themselves?

The Allied Power that had to enforce the Treaty of Versailles by themselves was France. Following World War I, the Treaty of Versailles was signed in 1919, primarily dictating the terms of peace with Germany. While the Allied Powers, including Britain, the United States, and Italy, were involved in the treaty negotiation, the enforcement fell largely to France.

France sought to ensure that Germany would comply with the treaty terms, including reparations and disarmament, as they were particularly concerned about future German aggression. The French military presence in the Rhineland and the utilization of the League of Nations to address violations were significant aspects of this enforcement. However, the lack of commitment from other powers, especially after the United States' refusal to join the League, left France as the principal enforcer in the years following the treaty's enactment.