As has been well documented, the 20's and 30's saw the establishment of numerous dictatorships and nationalistic-type governments throughout the world. Militarist Japan, Fascist Italy, Communist Russia, Nazi Germany, etc. Yet throughout this period, democratic ideas and rulers still managed to survive in some countries, and even make comebacks after WWII. So your challenge is to, with a period of no earlier than 1925, make Britain, France, and the United States (and other democratic countries of the time if you wish) fall to totalitarian-type governments ruled by either one man or a cabal of them.