World War I began on July 28, 1914, triggered by the assassination of Archduke Franz Ferdinand of Austria-Hungary. The conflict escalated due to a complex web of alliances, militarism, and nationalistic tensions among European powers. Initially involving Austria-Hungary and Serbia, the war expanded to include major nations worldwide, leading to unprecedented levels of destruction and loss of life. This cataclysm set the stage for significant geopolitical shifts, including the rise of new nations and the eventual emergence of World War II, profoundly altering the course of history.