Who: France, the United States, Britain, Ireland, Canada, Australia, New Zealand, South Africa, India, Belgium, Poland, Czechoslovakia, Germany, Italy and Japan all signed the pact.
What: The Kellogg Briand Pact. It was an agreement to outlaw war.
When: August 27, 1928.
Where: Signed in Paris, France.
Why: The pact was signed to try to stop wars like WWI from happening.