Who destroyed the windmill for the last time in the book "Animal Farm?"

The windmill was blown to smithereens by the humans. Frederick, the owner of Pinchfield farm, had cheated the animals out of their timber by paying with forged money. When Napoleon found out, he was stupefied and pronounced a death sentence on Frederick. He also warned the animals to prepare for another attack on the farm, considering the circumstances. Sentinels were placed all over the farm to keep watch.

When the attack came, the animals could not overwhelm the humans as easily as they had done during The Battle of the Cowshed, for Frederick and his men came prepared and fired at the animals as soon as they launched their attack. The animals had to flee and sought refuge in the farm buildings. They were at a complete loss. The humans had control of most of the pasture including the windmill.

Meanwhile Frederick and his men had halted about the windmill. The animals watched them, and a murmur of dismay went round. Two of the men had produced a crowbar and a sledge hammer. They were going to knock the windmill down.

Napoleon believed that it would be impossible for the men to knock the windmill down for the walls had been reinforced and were twice as thick as they had been before. However, it was Benjamin who realized what the men were up to, for those with the hammer and crowbar were drilling a hole at the bottom of the windmill. Benjamin commented:

‘I thought so,’ he said. ‘Do you not see what they are doing? In another moment they are going to pack blasting powder into that hole.’

The animals could not respond and:

Terrified, the animals waited. It was impossible now to venture out of the shelter of the buildings. After a few minutes the men were seen to be running in all directions. Then there was a deafening roar. The pigeons swirled into the air, and all the animals, except Napoleon, flung themselves flat on their bellies and hid their faces. When they got up again, a huge cloud of black smoke was hanging where the windmill had been. Slowly the breeze drifted it away. The windmill had ceased to exist!

This pernicious and vindictive act encouraged the animals and with ignited fervour, they viciously attacked the humans, driving them off the farm. They were victorious! There were great celebrations and the battle was named 'The Battle of the Windmill', but sadly, the windmill was gone forever. The animals' hard work had come to nothing. The windmill would later be rebuilt for a different purpose. instead of generating electricity, it would be used for milling corn.