One of the first things that many revolutionaries do is place the seed of unhappiness in the minds of the "people." In "Animal Farm" this is achieved through the character of the Old Major who is thought to represent the thinking of Marx/Engles. He points out to the animals how miserable their condition is under Jones, and how happy they will be when they control their own destiny. To solidify their revolutionary dreams, he teaches them a song, "Beasts of England," which becomes a mantra for them. (It's interesting that this is one of the things that Napoleon dismisses when he solidifies his power.)
Shortly after his speech, the Old Major dies. Who knows what the revolution would have looked like if he had lived; sadly, he does not, and the revolution and its ideals fall into the hands of the "practical" politician --- Napoleon (and Snowball for a while). The first thing they do is create the code of "Animalism." Much like the song, this gives the animals something to unify them as they develop the new and perfect world imagined by the Old Major.
None of this is particuarly "drastic" on the face of it; it is much more subtle, and that might be why it is so effective.