How the World and the U.S. Changed

The world experienced changes that shaped the 20th Century in post-World War I. Firstly, the United States became a superpower, rivaling even Great Britain at the time. Great Britain, in the other hand, reached its peak and slowly degraded towards second-class powers. Secondly, the countries of the Central Powers were broken up at the 1919 peace conference. Thirdly, genocide and poison gas were considered as acts of war.