They don't need a Hitler. Islam has 1.3 billion followers (which makes a big army if only ten percent are fundamentalists) and they have oil money and for 1,400 years they have been planning to convert all non-muslims, or subjugate them...or kill them.
They don't need armies, or airforces, or navies...they are scattered among ours.
And have already started to emerge, like the guy who tossed the grenade in the troops' tent in 2003..