When are the animals attacked by the humans again?

Three days later, Whymper informs Napoleon that the banknotes are forgeries. Napoleon sentences Frederick to death by boiling alive and tries to reconcile with Pilkington. The next morning, Frederick and his armed men overtake the farm. Napoleon considers calling Pilkington for help, but Pilkington sends a note that says, “Serves you right.” As the animals watch helplessly, Frederick and his men blow up the windmill. After that, the animals put up a fight and manage to chase the men off.