There is too much evidence to show that Napoleon used manipulation in his leadership. In light of this, I will give three examples.
First, in the beginning of the story, Snowball and Napoleon did not always see eye to eye. When it seemed that Snowball was becoming more popular, Napoleon used underhanded ways not only to discredit him, but to drive him off the farm. He made it seem that Snowball was collaborating with the enemy. He also said that Snowball is the one who destroyed the windmill. In short, Napoleon lied to gain the upper-hand.
Second, Napoleon also has Squealer, another pig, use technical, even scientific language to justify his actions of taking the apples and milk. Here is quote that says it all:
‘Comrades!’ he cried. ‘You do not imagine, I hope, that we pigs are doing this in a spirit of selfishness and privilege? Many of us actually dislike milk and apples. I dislike them myself. Our sole object in taking these things is to preserve our health. Milk and apples (this has been proved by Science, comrades) contain substances absolutely necessary to the well-being of a pig. We pigs are brainworkers. The whole management and organisation of this farm depend on us. Day and night we are watching over your welfare. It is for your sake that we drink that milk and eat those apples. Do you know what would happen if we pigs failed in our duty? Jones would come back! Yes, Jones would come back! Surely, comrades,’ cried Squealer almost pleadingly, skipping from side to side and whisking his tail, ‘surely there is no one among you who wants to see Jones come back?’
Even a brief look at the rhetoric is clear to show manipulation. Napoleon will do and say whatever it takes get what he wants.
Finally, Napoleon created the seven commandments. But the most pernicious thing about him is that he changed the commandments when it suited his needs. He was able to do this, because the other animals were not able to read. Hence, we have another example of manipulation.