How did international relations start at the beginning of the 20th century and in the 1920s and 1930s?

How did international relations start at the beginning of the 20th century and in the 1920s and 1930s? What new factors in world politics began to operate after the First World War?

At the beginning of the 20th century, relations in the world were considered imperialist. The leading role in world trade was taken over by the United States. On the world stage, contradictions were brewing, which resulted in the First World War. After that, a different world order was established. The dominant positions remained with the victors, and Germany and other defeated states were infringed upon. This provoked further outbreaks of aggression. There was also no unity between the victors, as they fought for domination in the world.