Quick aside, it's worth noting that the first big war of the 20th century began with an act of terrorism. So Franz Ferdinand wasn't particularly well-liked by his uncle, the Emperor Franz Joseph. Now that is a mustache. But even so, the assassination led Austria to issue an ultimatum to Serbia, whereupon Serbia accepted some, but not all, of Austria's demands, leading Austria to declare war against Serbia. And then Russia, due to its alliance with the Serbs, mobilized its army. Germany, because it had an alliance with Austria, told Russia to stop mobilizing, which Russia failed to do. So then Germany mobilized its own army, declared war on Russia, cemented an alliance with the Ottomans, and then declared war on France, because, you know, France.