Spoiler

- Education and training: Let's face it, for an armed forces it's size the Wehrmacht was second to none in training and education of it's soldiers, pilots and sailors.



- Equipment: The Wehrmacht had a huge amount of top of the line equipment for most of the war, particularly post-1943 when they possesed the best weapons of all warring factions, ironically that was when they were losing. However in '39-'41 the German arsenals weren't really that top of the line regarding tanks and anti-tank weaponry. They did have a disadvantage in Luftwaffe since they weren't able to produce enough Fw-190s (later Me262s) and were stuck with Bf 109s for most of the war (Already 5 years on it's neck by 1940)



Motivation: The soldiers were disciplined, and motivated to fight. During the early years it was to avenge the Versailles Treaty and the injustices it had imposed upon Germany. In the later years it was to protect the Fatherland from destruction, as many feared the Soviets would completly dismantle Germany if they won. This partially explains why 150 German divisions could withstand over 400 Soviet ones for 2 years against all odds.



Commanders: The Wehrmacht had lots of experienced and talented officers available, most of the senior ones had been officers already in WW1.



Doctrines: The combined arms, surprise and speed of German doctrines gave them a definite edge until the Allies learned how to counter it.