1940s: Up to 1945, virtually the entire world is at war. Germany and Italy battle the United States, Great Britain, Russia, and their allies for control of Europe, while in the Pacific region the United States continues the war against Japan.

Today: Europe is at peace. Former enemies Germany, Italy, Britain, and France are members of the European Community, with economic and political ties that make a future war between them virtually impossible. These countries are also members of the North Atlantic Treaty Organization (NATO) a defensive military alliance. Of other former enemies, the United States and Japan are allies, not adversaries.

1940s: Poland is at first under German control, then after World War II, although nominally an independent nation, it falls under Soviet domination. In 1955, Poland becomes a member of the Warsaw Pact, a military alliance between the Soviet Union and the communist nations...