Compare/contrast Old Major’s speech and the first four paragraphs of the Communist Manifesto.
In Animal Farm, the animals are not unlike the peasants of pre-Industrial times, who performed all the hard work on the estates and received few, if any, benefits other than sustenance. Since the Manifesto of the Communist Party was written in 1848, its premises cover not just the feudal system, but the "revolutionary reconstruction of society at large" such as that which occurred in France in which the 1789 Revolution virtually eliminated the aristocracy and the power of the clergy in the Catholic Church.
Nevertheless, as Engels and Marx, along with the Major, contend, there is truly a history of class struggle throughout life. The life of the animal as the proletariat is "one of misery and slavery," not unlike those industrial workers in the time of Engels and Marx, while Man as the bourgeoise capitalist is "a tyrant," for "he consumes without producing." Therefore, in order to remedy the state of the animals, the Major advocates "Rebellion."
Just as the animals have had one continuous struggle against the "tyrant," Engels and Marx observe that despite previous revolutions that annihilated aristocrats, men are yet involved in "class antagonisms" with the new class of capitalists, who also act as tyrants, collecting all the profits of their industry while the workers exist in deplorable conditions. They suggest, though, that with capitalism there is now a simpler division of classes than hitherto in the old systems such as existed with the feudal estates of France, for instance. This new class division of two classes, the capitalists and the workers--the bourgeoisie and the proletariat--parallels that of the animals and the farmers.