One of the signal blunders of the First World War was the German decision to tie itself to the strategic initiative of a weaker and more volatile partner in Austria-Hungary. There was nothing particularly compelling, for the Germans, in the Austrian cause in July and August 1914: the punishment of Serbia, albeit richly deserved by the Serbian state, affected no meaningful German interest. The same held true for the Russians, on the other side of the alliance structure, who seconded out their strategic purpose to the Serbs for no discernible end. Russian interests in the northern end of the Balkans were tenuous at best, but elite sentiment drives policy more than it ought, in 1914 and 2022 alike. Both the German and Russian empires, at the moment of decision, handed over their own initiative and interest to weak partners, and reaped the eventual annihilation of their own states in return.
The Germans ended up repeating this strategic error in the subsequent world war when they came to the rescue of their weaker and more erratic Italian partner — first in Greece and then in North Africa. The argument in favor of German action was stronger then than it was three decades prior, mostly because Italian defeat in Greece especially would have probably resulted in Britain trying to raise havoc across the Reich’s southeastern flank, whereas Austria-Hungary being rebuffed by Serbia, or even a Russo-Serbian combination, would likely not have appreciably diminished the German Empire. (I don’t believe the British would have made much of the opportunity, given their own uncertain performance throughout the war, but the point remains.) Nevertheless the close-run quality of Barbarossa — in hindsight lost in full with the narrow German failure to take Moscow in late-autumn 1941 — argues powerfully against the preceding months of unforced strategic diversion on a partner’s behalf.