Old Major, the prize Middle White boar pig of Manor Farm, died only three days after he called the animals together for his inspiring speech. During the meeting of the animals, Old Major called for them to revolt against their owner, Mr. Jones, and against all human control. He called on them to band together in perfect unity and comradeship against human subjugation. During his speech, Old Major made several important points that would serve as mottos for the animals. One was that "All men are enemies. All animals are comrades." In a similar statement, he claimed that "Whatever goes upon two legs is the enemy. Whatever goes upon four legs, or has wings, is a friend."

What is interesting is that all this works out quite differently in the end.  In the final chapter, the term "comrade" as a way for the animals to address each other is forbidden, and the "pigs" have taken on all the characteristics of the "men" who were enemies.  So the animals final state may be worse than their first.  They have new leaders who could care less about them, and they have been forbidden to be comrades to each other.  History may be a circle, but in their case it seems to be a descending spiral.

'All men are enemies. All animals are comrades.'

The simplistic attitude of Old Major shows that the concept of communism is indeed difficult to put into practice, as the farm animals will soon learn:

"...we are deluding ourselves if we think we are closer to those revolutionary ideas of justice, brotherhood, and equality than were the citizens of Stalinist Russia."

"...such descent from idealism to totalitarianism is inevitable in any violent revolution."

 - from 'Historical Setting for Orwell's Animal Farm'

   in enotes' 'Animal Farm Essays and Criticism'