By the end of Animal Farm, pigs are walking on two legs, Seven Commandments have become one, and the pigs insist to the other humans that all they wanted all along was to "to live at peace and in normal business relations" (10.27).
This ending is an allusion to the 1943 Tehran Conference, a meeting between U.S., U.K., and Soviet leaders (see "Symbols" for more about that). During the meeting, Winston Churchill (U.K.) and Franklin Roosevelt (U.S.) agreed to let Stalin have his way with Poland in exchange for military support in World War II. Many anti-Soviets in the West—like Orwell—saw this as betrayal on the part of the Westerners; from the communist perspective, it was dealing with the enemy. Everyone loses.
No wonder the animals can't tell the pigs and humans apart.