OTL during WW1 Germany widely overshadowed Austria-Hungary in the Central Powers and performed much better than them, becoming the dominant member and saving Austria-Hungary at critical points.
Try to come up with a way to reverse this so that the Germans perform very badly and suffer heavily to Allied forces, with the Austro-Hungarians performing highly competently and saving their floundering and ineffectual German allies, while Austro-Hungarian industry keeps the CP afloat in contrast to the poor efforts of their northern neighbors.
This war must still be a difficult struggle encompassing some length of time, utilizing an alliance structure which is preferably not excessively dissimilar to OTL (involving Austria and Germany on the same side at the very least) and the POD can stretch from 1900 onwards, with the war having to begin by 1920.
Extra points: Dissolving states of the German Empire at the end of this war try to join the stable Austro-Hungarians, who although defeated on the battlefield have no collapsed internally, unlike their poor northern neighbors.