Could you please relate Snowball's defeat and Trotsky's exile ?with references please reffering to KGB and the dogs
Snowball and Trotsky are paralleled in many ways, otherwise this would cease to be an allegory. One aspect of their similar natures was the desire to create committee. Trotsky was always developing Party or Army or Commissions to study and research society and its needs. This may have earned either favor with the masses, but their opponents who also struggled for the same power did not appreciate their ideas.
Trotsky was actually imprisoned for a time, exiled to Siberia and we later find him in Mexico continuing to speak out against what Stalin was doing.
I think with what we see occur on Animal Farm, Snowball was doing the same thing. Mollie eventually left, and Moses seemed to know what Snowball knew about what Napoleon was doing.
The Cheka were the police force at the time of Trotsky's exile. This group later turned into the KGB, but were trained in secret just like Napoleon's dogs.
Trotsky was eventually taken out by a hit man, we never really hear about Snowball.
As your question implies, Snowball stands for Leon Trotsky. Napoleon stands for Joseph Stalin. The way that Snowball is exiled resembles what happened to Trotsky in real life.
Trotsky was a rival of Stalin's for power. They had somewhat different ideas and they both wanted to take power after Lenin's death.
However, Stalin managed to maneuver himself into a position where he held the power as Lenin weakened. He managed to reduce support for Trotsky by persuasion, but also by purging the party of Trotsky supporters (this is where the dogs come -- this is similar to them threatening anyone who seems to agree with Snowball.