After World War I, 1. Four empires collapsed: the German Second Empire, the Austro-Hungarian Empire, the Ottoman Empire and the Russian Empire.

2. The old empire, Britain and France, was greatly weakened, but still dominated the international alliance.

3. The United States made a war windfall, and the global financial center shifted from London to new york, but it did not gain the world dominance politically.

4. After the establishment of the Soviet Union and repelling the interference of imperialist countries. War wounds and urgent difficulties need to be solved urgently.