When the GDR was rebuilding its military they mostly drew officers from German antifascist fighters in Spain. They did fill in some gaps from Wehrmacht officers who were cycled out very quickly. A good source on this is Viktor Grossman’s A Socialist Defector. He is anti-Stalin (nobody’s perfect, and it doesn’t come up much in the book), but he does support the idea of what the GDR was trying to accomplish overall and how horrible the Wende was