War is Peace

In 1984, Oceania is always at war with someone whether it is Eastasia or Eurasia. If they are at war with Eastasia then they have always been at war with Eastasia and never with Eurasia. Similarly, if they are at war with Eurasia then they have always been at war with Eurasia and never with Eastasia. This is what the people have to beleive even though they switch enemies every few years.
The same thing happens in Animal Farm but with the two neighboring famrs instead of neighboring countries. Napoleon is trying to sell a load of timber to the best buyer and Mr. Pilkington and Mr. Frederick are in the running. He is nicer to the one that he thinks will get the timber. He started being freindly to Pilkington and told horrible stories of what Frederick did to his animals. He spread words like "Death to Frederick", but eventually, he sold the timber to Frederick claiming that being nice to Pilkington made Frederick raise his price. He changed the slogan to "Death to Pilkington" and cut off all ties with the farm.
In both situations, the leader changed around enemies because he could and pretended that nothing had changed at all. Everything had always been this way.