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. Germany's war plan, the Schlieffen Plan, required that it invade France in the most expedient way possible, which as you can see is via Belgium. And Great Britain was a friend of Belgium, I mean as much as anyone can be a friend of Belgium, and so they declared war on Germany. So by August 4th, all the major powers of Europe were at war with each other.