What was the catalyst to World War1 ?

The act that sparked the hostilities was the assassination of Archduke Ferdinand of Austria.

Thank you!

You're welcome.

The catalyst to World War 1 was the assassination of Archduke Franz Ferdinand of Austria-Hungary. This event took place on June 28, 1914, in Sarajevo, when the Archduke and his wife were shot by a Bosnian Serb nationalist named Gavrilo Princip.

To find this information, you can start by searching for "What was the catalyst to World War 1?" on a search engine like Google. One of the top results will likely provide you with a brief summary of the event. Additionally, you can explore historical sources, books, or articles that delve deeper into the causes and events leading up to World War 1.