| 1921 | New Economic Policy in Soviet Union |
| 1922 | Mussolini seizes power in Italy |
| 1924–1929 | Buildup of Nazi Party in Germany |
| 1925 | Hitler, Mein Kampf |
| 1927 | Stalin comes to power in Soviet Union |
| 1928 | Stalin’s first five-year plan |
| 1929 | Start of collectivization in Soviet Union; Lateran Agreement |
| 1929–1939 | Great Depression |
| 1931 | Japan invades Manchuria |
| 1932–1933 | Famine in Ukraine |
| 1933 | Hitler appointed chancellor in Germany; Nazis begin control of state and society |
| 1935 | Mussolini invades Ethiopia; creation of U.S. Works Progress Administration as part of New Deal |
| 1936 | Start of great purges under Stalin; Spanish Civil War begins |
| 1936–1937 | Popular Front government in France |
| 1939 | Germany occupies Czech lands and invades Poland; Britain and France declare war on Germany, starting World War II |
| 1940 | Japan signs formal alliance with Germany and Italy; Germany defeats France; Battle of Britain |
| 1941 | Germany invades Soviet Union; Japan attacks Pearl Harbor; United States enters war |
| 1941–1945 | The Holocaust |
| 1944 | Allied invasion at Normandy |
| 1945 | Atomic bombs dropped on Japan; World War II ends |