Do these have to be general or specific? Here are five. [Besides aspects such as Hitler's 'leadership'..]
1.Gross numerical inferiority (For instance, by the Soviet Vistula>Oder offensive in January 1945, the ratio in infantry was 11:1, armour 7:1 and 20:1 in artillery.)
2.Tactical indecision. (As seen in Fall Bleu, the German 1942 summer offensive, with Hitler wavering between Stalingrad and the Caucaus).
3.The Blitz. (The beginning of this offensive diverted luftwaffe forces from bombing RAF airfields, thus allowing the British airforce to recover and seize victory in the Battle Of Britain.)
4.The Holocaust. (Besides being a campaign of sheer barbarity, the Holocaust diverted many resources which could have potentially been used to strengthen the military. Additionally, the atrocities committed within occupied territories strengthened support to continue fighting the war, as well as resulting in partisan movements..)
5.Destruction of German infrastructures. (Largely through bombing, this prevented further mass production, weakening the Wehrmacht and Luftwaffe greatly..)
In one sense, German defeat was virtually inevitable from 1941, with Operation Barbarossa being a doomed offensive. (Although there were points where Stalin wanted to surrender..)
On what day was Joseph Goebbels appointed Reich Minister For Propaganda and Popular Enlightenment?