What happens in the battle of the windmill?

In the Battle of the Windmill, the farmers attempt to blow up the windmill the animals have been building to supply electricity to the farm. Frederick had recently purchased wood from the farm using counterfeit money, and his greatest desire is to take the farm for himself. Napoleon warns the animals to expect, and when Frederick arrives to blow-up the windmill using gunpowder, the animals drive him away. Snowball is shot and is awarded "animal hero first class".