What happened when Archduke Francis Ferdinands assassination triggered World War 1?

The assassination of Archduke Francis Ferdinand of Austria on June 28, 1914, set off a chain reaction of events that led to World War I. Austria-Hungary issued an ultimatum to Serbia, where the assassin was linked, leading to Serbia's partial rejection of the demands. This prompted Austria-Hungary to declare war on Serbia, which activated a complex web of alliances involving major powers like Russia, Germany, and France, ultimately escalating into a full-scale global conflict. The war, characterized by trench warfare and massive casualties, lasted until 1918 and significantly altered the political landscape of Europe.