Dr. Halford Mackinder reasoned that land based authoritarian political regimes "in the heartland" are superior in warcraft to littoral based Republics. His works (cited below) explain why this is the case.
Brief Example of his reasoning:http://amzn.com/0465013325
Foreign Affairs Publication: The Pivot of History. https://www.foreignaffairs.com/articles/
Wikipedia Review: http://en.wikipedia.org/wiki/Halford_Mackinder