In 1882 Germany, Austria-Hungary and Italy formed the Triple Alliance. The three countries agreed to support each other if attacked by either France or Russia. France felt threatened by this alliance. Britain was also concerned by the growth in the German Navy and in 1904 the two countries signed the Entente Cordiale (friendly understanding). The objective of the alliance was to encourage co-operation against the perceived threat of Germany.

Three years later, Russia, who feared the growth in the German Army, joined Britain and France to form the Triple Entente. In contrast to the Triple Alliance, the terms of the Entente did not require each country to go to war on behalf of the others, but stated that they had a "moral obligation" to support each other. The Russian government was also concerned about the possibility of Austria-Hungary increasing the size of its empire. It therefore made promises to help Serbia if it was attacked by members of the Triple Alliance.