The Depression of the Thirties did not cause the government to shrink. Nor did it shrink during the short periods between wars (1945-50, 1953-1960, 1976-1990, 1993-2001) There were minor wars in those gaps: Grenada, Panama, Somalia, Salvador and Nicaragua, Bosnia, and all sorts of interventions and smaller meddlings.
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Perhaps if we actually were at peace for a serious period of time, we could get by with less growth in government.