The first World Cup is held in Uruguay; the hosts win the title, beating Argentina 4–2 in the final.
The New York stock market collapses in late October, heralding the Great Depression that spreads around the world.
Germany invades Poland, starting the deadliest conflict in human history, which ends with Japan's formal surrender on 2 September 1945.
The peace treaty ending the war between Germany and the Allies is signed in the Hall of Mirrors, imposing war guilt, territorial losses and heavy reparations on Germany.
An H1N1 influenza pandemic spreads worldwide, killing tens of millions of people, one of the deadliest pandemics in history.
Roosevelt, Churchill and Stalin meet at Yalta to discuss the post-war reorganisation of Europe and the world.
The UN Charter enters into force after ratification by a majority of signatories.