The most glaring comparison is the relationship between Napoleon and Snowball. Napoleon is Stalin, while Snowball was Trotsky. This can be seen in a few ways.

1. Snowball(trotsky) wants to spread the revolution outside the farm, while Napoleon(Stalin) wants to focus on internal issues.

2. Snowball is described as a better orator and persuader during the official meetings, while Napoleon is better at gaining allies backstage, which was true in real life.

3. Snowball comes up with the plans for the windmill, which Napoleon is dismissive of. However, once Snowball is gone, Napoleon co-opts his idea, which is comparitive to the economic policies put forth by Trotsky and Stalin's responses.

4. Stalin eventually ousts Trotsky, which also happens in the book. Napoleon(Stalin) then launches a smear campaign against Trotsky, ruining his image in the eyes of the populace.