The German Federal Army (German: Deutsches Bundesheer) was the military arm of the German Confederation from 1815 to 1866 whose purpose was the defence of the Confederation against external enemies. Although the Congress of Vienna in 1815 decreed the formation of the army and delimited its size and purpose, no work on its formation was begun until 1841, after the Rhine crisis brought the threat of war to Germany. Even then, only preliminary work was accomplished on troop readiness. Most work focused on the building of federal fortresses.