I chose alliances as the most impactful cause of WW1 for many reasons. My first reason being that the whole war wouldn't have escalated to the point that it did if people didn't have alliances, it would've just been a war wit Serbia and Austria-Hungary if alliances didn't exist. My other reason is that the alliances led to power and weaponry being spread quickly among the allied nations, countries like Italy would join alliances for the said power that could come from them, this led to the war being drawn out more and the alliances stripping away power from each other. Finally, the alliances drew out the war a lot, it may of ended quicker if it was just Serbia and Austria-Hungary, but other countries joined in and eventually they started fighting for their own ideals instead of fighting for Serbia, like how the USA joined to fight for democracy, but not really to fight with Serbia whom they were allied with. Overall, the war wouldn't have started or had been drawn out as long if it hadn't been for alliances.