A good way to describe the Battle of the Cowshed from "Animal Farm" is that it was the animals' final required act to take over the farm from Mr. Jones. Although some of the animals were killed or wounded, the majority survived. The battle also led to the establishment of a hierarchy and allowed Napoleon to further exercise power over the other animals.
In essence, the Battle of the Cowshed was a pivotal moment for the animals that ultimately led to them "evolving" into human beings. "Animal Farm" was written by George Orwell in 1945, and the battle that occurs between Mr. Jones and the animals is based on Orwell's observations of the Russian Revolution of 1917.
The novel features two different power structures on the farm. In the beginning of the book, Snowball and Napoleon, two pigs that live on the farm, take control of the farm but exercise very little power beyond setting some basic rules. They also draft commandments that declare all animals to be equal.
When a plan to build a windmill ultimately fails, Napoleon blames Snowball and kills any animals he suspects of working with him. Napoleon is then able to rule the farm on his own, and he changes the Seven Commandments of Animalism to only include the statement "all animals are equal, but some animals are more equal than others."
At the end of the novel and several years later, the animals realize they have begun to resemble humans under Napoleon's leadership. That is, by altering the tenets of Animalism, the animals have undergone a permanent change and are now homogeneous.