Here is evidence for the Roberts Higgs thesis and, if I recall correctly, some recent remarks by Thomas Piketty on revolution and tax progressivity (does anyone know the link?). Juliana Londoño Vélez writes:

Abstract I argue that progressive income taxation in the twentieth century is a product of the exigency of war and not of democracy. I obtain long-run series of the top marginal personal income tax rate for a large sample of OECD countries, and use data on wars of mass mobilization and democracy from the Correlates of War data set and Scheve & Stasavage (2012) to test this hypothesis. My results suggest that wars of mass mobilization (i.e. wars in which more than 2% of the population served in the military) cause substantial increases in tax progressivity. These effects are persistent and do not vanish upon the conclusion of war.