How is Animal Farm a satire on the Russian Revolution?

Animal Farm is a satirical allegory,
so all the characters in the story are representative of someone or some group that was
key in the Russian Revolution.  Comparisons are as
follows:

• Old Major:  Karl
  Marx


• Napoleon:  Joseph
  Stalin


• Snowball:  Leon
  Trotsky


• Squealer: 
  propaganda


• Boxer and Clover:  loyal
  masses


• Benjamin: 
  skeptics


• Nine Dogs of Napoleon: KGB (secret
  police)


• Moses: 
  religion


• Mr. Jones:  Czar Nicholas
  II

In addition to the characters, the concept
of animalism as defined by Old Major in the novel is similar to the concept of Marxism. 
The characters in the novel have traits and perform actions that are similar to those of
their historical counterparts.  For example, after Napoleon runs Snowball off the farm,
he asks all the animals to confess their dealings with him.  After these confessions,
Napoleon has the animals killed by the dogs.  This is representative of Stalin's
treatment of those who were caught, tortured, and forced to confess only to be killed by
the KGB for harboring secrets against the state.  The novel may be considered a satire
because it shows how ridiculous the behaviors of the animals are as they attempt to
throw Animalism aside to gain power and control (i.e. the pigs walking on two legs while
with the humans).