Between fiscal years 1945 and 1948 inclusive federal spending declined 67.85%, from $92.7 billion in 1945 to $29.8 billion in 1948. By the end of fiscal 1952 spending increased back up to $67.7 billion, but still 27% lower than in 1945.
Real GDP declined 9.4% from January 1945 to January 1949, but rebounded 28% by the time he left office four years later.
Who says we can't cut the size of government dramatically and still grow like gangbusters?