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Squealer was able to trick the uneducated masses to believe that everything Napoleon said was in the best interest of the farm and animals. He changed and eliminated commandments in the fashion that gave Naopoleon more power. For example, one important commandment in Animalism was no "No animal shall hurt another animal." When animals disobeyed him, Napoleon knew he needed to punish them with brutal force in order to gain total power. He was able to get away with it because Squealer conjured up elaborate stories that made the animals who suffered at the hands of Napoleon look like enemies and threats to the farm's safety and, therefore, justly punished. This exonerated Napoleon and made the need to ammend the commandment seem necessary.
He also used scapegoating techniques (techniques to put blame on innocent individuals) to take the animals' attention away from all of Napoleon's evils and focus them on Snowball. By eliminating all political competition, Napoleon stood alone as the leader of Animal Farm.