So by August 4th, all the major powers of Europe were at war with each other. By the end of the month, Japan, honoring its alliance with Britain, would be at war with Germany and Austria as well. When all was said and done, counting colonies and spheres of influence, the world map would eventually look like this. You'll never guess who wins. So there were many opportunities not to mobilize and declare war, none of which were taken. Some blamed the web of alliances itself, which is what Woodrow Wilson wanted to fix with the League of Nations. Some blamed Russia, the first big country to mobilize.