Maybe it has allready been answered, but I'd say "Vernichtungskrieg" (war of anihilation).
But I am not sure wether this term is really contemporary, meaning actually used during WW2 or having been invented after WW2 to describe the eastern front.
Regarding US WW2 strategy, the term "Abnutzungskrieg" was used (war of attrition) while soldiers called it "der Krieg des reichen Mannes" (rich man's way of war).
__________________
|