Squealer takes the central role in making announcements to the animals, as Napoleon keeps appearing less and less often as the book progresses.
Orwell uses Squealer mainly to show how the increasingly totalitarian and corrupt regime uses propaganda and deceit to get its ideas accepted and implemented by the people.
He takes advantage of their malleable minds and moulds them to his liking — the dogs show up later as military enforcers or secret police.
The animals experience a vague feeling of unease, and when Clover and Muriel ponder the changes, they are told that they have simply forgotten.
Terror and silver-tongued oration fool nearly everyone, and the sole animal who sees through these fronts, Benjamin, is simply too cynical to do anything.
This reflected Orwell's view that events in Russia following the Revolution of 1917 had followed an unwelcome path, and that the egalitarian socialism he believed in had there become a brutal dictatorship built around a cult of personality and enforced by terror and lies.