In the meeting about the windmill, Snowball is arguing that the windmill will free the animals from the need to work. Napoleon, who disagrees with Snowball about the need for the windmill, calls in nine dogs to chase Snowball from the farm.
This episode in the book is meant to allude to the struggle for power between Josef Stalin and Leon Trotsky after the death of Lenin. Stalin eventually drove Trotsky out of the Soviet Union and into exile. After Trotsky was exiled, his name and his ideas were deleted from all Soviet histories.
The windmill would appear to be Snowball's pet project; he argues eloquently in favour of it, declaring that if it were established on the farm, it would bring great benefits. Napoleon however insists that the animals should concentrate on food production. This clash between the two reaches a head during a heated meeting which ends with Napoleon calling upon his great guard dogs to chase Snowball from the farm.
This occasion sees the first major use of brute force by Napoleon: something that will become a characteristic of his rule. The dogs had been nurtured by Napoleon in secret, and now he unleashes them against Snowball, his chief rival. He does this because there was a real chance of the animals voting in favour of the windmill, thus undermining his own position. This incident shows, for the first time, that Napoleon is more than willing to resort to force to get his own way, contravening the principles of an open and democratic society upon which Animal Farm was initially founded. The alarming spectacle of Snowball being chased off the farm sets the temper for Napoleon's increasingly brutal and perverted rule.
However, this is not all. Only days after this meeting, Napoleon decrees that the windmill will be built after all. Insidiously, he gets his chief propagandist Squealer to declare that the plans for the windmill were really Napoleon's and that Snowball had stolen them. The reverse is true, but this is the beginning of the falsification of history that will also be a major feature of Napoleon's rule. He has no qualms about using force and also about lying to discredit his rivals.
The windmill incident and the elimination of Snowball recall the true-life events of Soviet history when Josef Stalin and Leon Trotsky were engaged in a bitter power-struggle. Trotsky, like Snowball, was inventive, a brilliant speaker and enjoyed mass popular appeal. Stalin, like Napoleon, was more of a ruthless schemer and got rid of Trotsky by use of lies, tricks, and force. Having defeated his great rival, Stalin went on to portray him as the enemy of the Soviet Union, as Napoleon later made Snowball out to be the enemy of Animal Farm. Stalin, indeed, did not stop there, but had Trotsky assassinated in exile in distant Mexico.