I actually meant in the 1930's and 40's. My bad. According to the CIA Factbook, Catholicism is now the largest single denomination in Germany at 34%. Protestant denominations are not broken out, but account for 34% in total. Wikipedia has it at 30% Catholic, and 33% protestant along with 5% Muslim, but 55% say they are "non-religious," especially in the east.
Prussia became East Germany after the War, and atheism prevailed.