In the book animal farm, Orwell very carefully created his characters in order to mimic certain political figures of the time. In this case Squealer functioned as the propaganda department. Squealer uses language to keep Napoleon in power. He uses language as a means to consolidate power, in this light truth is an element that can be manipulated through language.
His use of language is designed to enhance the control that the pigs have over the rest of the farm. When squealer uses language as his weapon he constantly puts particular spins on events and conditions and he uses slogans and such to help control the other animals. He pleads with the animals for example, to think of how Napoleon is just watching out for them. Napoleon would hate it he says, if they fell for Snowballs tricks. Here squealer is trying to get the animals to identify with Napoleon and feel grateful for him. He also uses slogans like “Tactics comrades tactics” to drum ideas into their heads rather than having them think about anything. So by spinning the things that happen, and giving the animals slogans instead of explanations, Squealer helps to keep them under control.
One of the ways the pigs rewrite history is to ensure that they are always in control; of course this job falls largely to the hands of Squealer. The pigs rewrite history by being able to stretch the truth so that the animals, unassuming of the ulterior motives, end up believing what Napoleon, Squealer and the other pigs say is right. An example of this would be when the pigs move into the house and while it might on face value violate a tenet of animalism, Squealer agues that it is needed for the Pigs to have space in order to work and plan for the farm benefit. This an example of the rewriting history, in order for the pigs to benefit while the other animals fail