Which event is recognized as the immediate trigger for World War I?

The assassination of Archduke Franz Ferdinand of Austria is recognized as the immediate trigger for World War I because it set off a chain reaction of political events that escalated tensions among the major powers in Europe. On June 28, 1914, Ferdinand was killed by Gavrilo Princip, a member of the Serbian nationalist group known as the Black Hand. This assassination heightened existing geopolitical tensions, leading Austria-Hungary to issue an ultimatum to Serbia, which, when not fully accepted, resulted in Austria-Hungary declaring war on Serbia. This action activated a complex web of alliances and mutual defense agreements, drawing multiple countries into the conflict and ultimately leading to a full-scale war.

While other events such as the sinking of the Lusitania or the declaration of war by Germany were significant in the broader context of World War I, they were not the events that directly triggered the start of the war. The bombing of Sarajevo, while related to the assassination, is not the same as the act of assassination itself, which directly caused the diplomatic crisis that followed. Thus, the assassination serves as the crucial, immediate catalyst for the war’s outbreak.