What are the themes of Chapter 4?no

I suppose the theme of Chapter 4 is the relationship
between Animal Farm and the outside world.

In this chapter,
the revolution on Animal Farm is influencing the farms in the surrounding area.  Other
animals are wondering if they should do the same as Animal Farm
did.

Because this kind of thinking is a big worry to the
human farmers, they decide to do something about it.  That is, they decide to attack
Animal Farm to defeat the revolution and prevent it from
spreading.

For later in the book, it is important to note
that Snowball is the leader of the defense of the farm.