From the OSS (CIA) 1943 psychological profile of Hitler: His primary rules were to never allow the public to cool off; never admit a fault or wrong; never concede that there may be some good in your enemy; never leave room for alternatives; never accept blame; concentrate on one enemy at a time and blame him for everything that goes wrong; people will believe a big lie sooner than a little one; and if you repeat it frequently enough people will sooner or later believe it.

One of my favourite documentary series of all time. Some of the senior Nazis were still alive when they filmed it and they managed to interview them.