Mollie defects, the windmill debate divides the farm, and Napoleon expels Snowball using the trained dogs.
As winter approaches, Mollie becomes increasingly difficult. She arrives late to work, leaves early claiming stones in her hooves, and spends time staring at her reflection in the drinking pool. Clover sees her talking with a man from Foxwood over the hedge and allowing him to stroke her nose. When confronted, Mollie denies it and cannot look Clover in the eye. Clover searches her stall and finds a hoard of ribbon pieces and a lump of sugar. Mollie disappears. A few weeks later, pigeons report she has been seen in Willingdon, in ribbons, drawing a cart for a fat red-faced man.
The winter is bitter and the animals cannot work in the fields. They attend Sunday meetings and the pigs plan the coming season. Napoleon and Snowball disagree on every question: the defence of the farm, the size of the grazing field, whether to train the animals to use firearms. Napoleon is better at canvassing animals between meetings, particularly the sheep. Snowball is the better public speaker.
Their greatest dispute is about the windmill. Snowball proposes building one on the highest point of the farm to generate electricity, which would power machinery, heat the stalls, and reduce working hours to three days a week. He designs detailed plans on the floor of the shed, consulting books from the farmhouse. Napoleon comes once to look at the plans and urinates on them without comment.
Napoleon argues that the farm should focus on food production rather than a difficult construction project. The farm divides into factions: those who chant "Vote for Snowball and the three-day week" and those who chant "Vote for Napoleon and the full manger." The only animal who does not take a position is Benjamin.
At the decisive Sunday meeting, Snowball gives a passionate speech on the windmill and wins the vote. Then Napoleon stands, casts a peculiar sidelong look at Snowball, and utters a high-pitched whimper. Nine enormous dogs in brass-studded collars burst through the door. They chase Snowball across the farmyard and through a hedge, and Snowball is never seen again.
Napoleon announces that Sunday meetings are abolished. Henceforth, a pig committee under his supervision will decide all questions of farm policy and communicate their decisions to the others. There will be no more debates. Four young pigs try to protest but the dogs growl and silence them. The sheep bleat "Four legs good, two legs bad" for fifteen minutes.
Squealer makes the rounds afterwards to explain. Napoleon has not really opposed the windmill: it was always his idea, and Snowball stole it. He only appeared to oppose it in order to lure out those sympathetic to Snowball, and to get rid of a dangerous influence. This is what is called "tactics." Most animals accept this explanation. Boxer begins to say "Napoleon is always right" alongside his original motto.
Three weeks later, Napoleon announces they will build the windmill after all. Rations will be reduced to fund it.
Mollie's departure in the chapter's opening is a structural parallel to Snowball's expulsion at its close. Both characters leave the farm in this chapter; both represent losses that the novel does not present as gains. Mollie's choice is selfish and ideologically vacant; Snowball's removal is forced and ideologically catastrophic. But both departures reduce the farm: one removes a horse who would have become a burden, the other removes the farm's best mind.
The windmill debate is the novel's central political confrontation. Snowball presents his case with genuine intellectual energy: the plans are detailed, the argument is coherent, and the vision of leisure time and mechanisation is persuasive. Napoleon offers only opposition, never an alternative. This mirrors the strategy of the authoritarian politician who wins not by having a better idea but by destroying the credibility of competing ideas, and then, once the threat is removed, adopting the idea as his own.
The signal -- "Napoleon stood up and, casting a peculiar sidelong look at Snowball, uttered a high-pitched whimper of a peculiar kind" -- is among the most carefully written sentences in the novel. Every word contributes to the sense of premeditation: Napoleon's look at Snowball specifically, the qualification of peculiar applied twice, the mechanical response that follows. The expulsion has been planned for months. The debate was never real.
Napoleon's abolition of Sunday meetings is the novel's most direct move toward authoritarian control, and the sheep's fifteen minutes of bleating is Orwell's darkest comedy: the slogan that was supposed to unite the animals against human tyranny is now used to suppress the animals' own speech. Language has been turned against the community it was designed to protect.