Well I am just going by the view of the Common German Soldiers and Officers who fought on the Eastern Front.
I agree they were badly led, badly armed, badly supplied, but they were not lacking in courage and a resilience to conditions that even the Germans found hard to bare.
re :On longer scales, the claim is directly falsified - tyrannies lose wars to republics much .
Which claim is this.
If its this.
The Germans and Soviets when well led made better soldiers, coming from dictatorships where life was cheaper, they were able to withstand the horror and death of war. many also were brought up in martial environments the Hitler Youth and Kommosol both had a strong death and glory cult
I stand by it, and its a claim that many Allied senior soldiers on the British and American side made.