Austria, of course; as the minor partner, Austria benefited from Spanish backing all the way up to 1648.
All that Spain got from this implication in Central-European affairs was:
- Material impoverishment: the riches that were obtained from the American possessions were spent in the religious wars fought in Germany.
- Complete spiritual impoverishment: as a result of having assumed the dignity of HRE emperor, Charles I/V started a policy that was later to be followed by his son Phillip II and afterwards by all the line of Spanish Hapsburg kings, consisting of defending the Catholic faith against Protestantism. As a result, religious extremism followed and as the years passed Spain lost all contact with the new cultural and scientific tendencies that took place in Europe, as the only way of keeping the country religiously unified was to shut it from outer influences.
(I know this is a bit oversimplistic, but I find it boring and unnecessary to support the above by filling this post with lots of dates & names...all who knows will fill in the blank spaces!)
BTW, what about Spain having war waged against her by her former ally when Austria found she didn't agree with Charles II testament?
Cheers