Old Major dying could be an allegory for either Lenin's death or Marx's.
The animals chasing off the humans is an allegory for the February Revolution in Russia.
Snowball/the pigs stepping up to lead is an allegory for the October revolution when Lenin stepped up to lead.
When Jones comes back and the animals chase them off, represents the Civil War.
Old Major's Skull being dug up and placed for viewing most likely and allegory for indoctrination (getting the animals to "think" they were doing what old major wanted).
Yes comrades, we must honor Major
The dogs were an allegory for Lenin's secret police.
