Births on April 21

Don Cornell, American singer and trumpet player (d. 2004)

Don Cornell (born Luigi Francisco Varlaro; April 21, 1919 – February 23, 2004) was an American singer.

5 Jan

Nazi Party
The German Workers' Party, which would become the Nazi Party, is founded.
23 Mar

Italian Fascism
In Milan, Italy, Benito Mussolini founds his Fascist political movement.
4 May

Treaty of Versailles
May Fourth Movement: Student demonstrations take place in Tiananmen Square in Beijing, China, protesting the Treaty of Versailles, which transferred Chinese territory to Japan.
19 May

Turkish War of Independence
Mustafa Kemal Atatürk lands at Samsun on the Anatolian Black Sea coast, initiating what is later termed the Turkish War of Independence.
29 May

General relativity
Albert Einstein's theory of general relativity is tested (later confirmed) by Arthur Eddington and Andrew Claude de la Cherois Crommelin.