Old Major used the power of language to influence the other animals into wanting to start a rebellion; by using key words to trigger their anger such as over worked and lack of food.
The 7 commandments
The following night old major died in his sleep. Two of the oldest pigs stepped forward to then lead the rebellion and continue on with Old Major's initial plan (to over throw their master Jones).
The animals worked together to expel Jones with snowball leading them to victory. Napoleon and squealer the other pigs were nowhere to be seen. Napoleon and Snowball fought lots this was because Napoleon was jealous of him so later he expels him too, much to the other animals confusion.
Animals or Humans?
The 7 commandments were composed as the rules of Animal Farm. These were the laws that were to be followed by all animals they could be summed up by " 4 legs good 2 legs bad". Through out the story Napoleon alters them and misguides the animals into believing he is right through his mouth piece squealer.
Napoleon takes the credit for Snowballs idea of the windmill and after he gets rid of him he begins to use his ideas to create one. This is destroyed several times by the weather but Napoleon instead tricks the animals into believing Snowball was behind the misfortune.
"As the animals outside looked from pig to human and from human to pig and back again they could no longer tell which was which." This quote from the end of the story shows us that the pigs changed so much they become clones of humans. The animals no longer knew who they were looking at because they were both corrupted by power.