Hat tip to the Mises Institute. From the Foreword to the German Edition of Keynes’ General Theory:
The theory of aggregate production, which is the point of the following book, nevertheless can be much easier adapted to the conditions of a totalitarian state than the theory of production and distribution of a given production put forth under conditions of free competition and a large degree of laissez-faire. This is one of the reasons that justifies the fact that I call my theory a general theory. –John Maynard Keynes, 1936.
Full article at the Mises Institute: https://mises.org/library/keynesianism-loves-total-state.