The windmill is actually destroyed and rebuilt several times throughout the course of Animal Farm. The first windmill collapses in a storm, and the second windmill is blown up during the Battle of the Windmill. After the first windmill is destroyed, which Napoleon blames on Snowball’s sabotage, the animals begin reconstruction and make the walls much thicker. After the second windmill is fully built, Frederick attacks Animal Farm and takes down the structure with blasting powder. Undeterred, the animals begin rebuilding the windmill the next day.