The battle starts when a large group of farmers (including farmer John) show up with intentions of recapturing the farm. However, Snowball (the pig) has been expecting something like this for a while and has, in the manner of the humans, already made a plan of defense. First the birds attack; pigeons peck at the invaders from the sky, and geese attack them from the ground. This is meant as a diversion as Snowball and the sheep charge. After the charge, the humans appear to be beating back Snowball and his band of sheep, and they retreat into the yard. However, this is merely the master stroke of Snowball's plan, as the men are cut off from behind in an ambush with all of the heavy animals of the farm. In the resulting chaos, a stable boy is knocked out (supposed dead by the animals) and the humans flee. As they flee, the animals reveal one of their more animalistic traits, attacking the fleeing humans with abandon as they give voice to their pent up rage and thirst for vengeance. At this point, Boxer (the horse that struck the boy) begins to feel remorse for 'killing' the boy, as he did not mean to do such a thing. However, Snowball urges him to overcome his remorse stating that the "only good human is a dead human". After that, the animals discover that Mollie is missing and goes to look for her. While they are looking for her, the stable boy wakes up and flees.
This battle gives a focus of the Revolution to the animals and they celebrate its anniversary in the years to come.