How did World War 1 begin and what event caused World War 1?

World War I began on July 28, 1914, following the assassination of Archduke Franz Ferdinand of Austria-Hungary by Gavrilo Princip, a Bosnian Serb nationalist. This event triggered a series of diplomatic crises and alliances, leading Austria-Hungary to declare war on Serbia. The complex web of alliances in Europe then pulled multiple nations into the conflict, escalating it into a global war. Ultimately, the assassination is widely regarded as the immediate catalyst for the war.