Unfortunately, Serbia was in an alliance with Russia, so the Russian threatened to to declare war on Austria-Hungary. At this point, the war was still preventable, if both sides stepped down, it could have been averted; however, the Russian army began mobilizing before the end of the one month time limit on the ultimatum, so the Germans, who were allied with the Austrians, stepped in, fearing a direct Russian invasion.

The French and the Russians had signed a political and military pact in 1894, and the Germans were wary of this. Although the Germans openly demanded French neutrality, they had already arranged for the Schlieffen plan, deploying 80% of its forces on a potential Western Front. To invade France, they passed through Belgium, which had signed a mutual protection treaty with Great Britain, which in accordance with the treaty, entered the war on the behalf of the Belgians.