This event repeats every year forever
Though there are many perspectives about the beginning of hostilities the 28th of July was the first military action with the Austria-Hungarian Empire's shelling of the Serbian capital of Belgrade. In the coming weeks and years additional countries discovered reasons to join in the conflict and picked sides they would support. Many of these subsequent choices were made due to written treaties and positioning in the international arena. Some choices were specific to land grabs or other regional issues and had little impact on the conflict occurring in central Europe.