For Marx and Engels, the fundamentals of class conflict have not changed since Rome and Middle Ages. Class antagonisms have underscored the progression of human society. Marx and Engels make clear that settings such as Rome and Middle Ages might have had different vocabulary to describe it, but the reality of the "insiders" and "outsiders" were present:
The history of all hitherto existing society is the history of class struggles....Freeman and slave, patrician and plebeian, lord and serf, guild-master and journeyman, in a word, oppressor and oppressed, stood in constant opposition to one another, carried on an uninterrupted, now hidden, now open fight, a fight that each time ended, either in a revolutionary reconstitution of society at large, or in the common ruin of the contending classes.
Terms like "Patrician and plebeian" or "lord and serf" are no different than "oppressor and oppressed." Marx and Engels believes that the constant antagonism and outright dominance between those who have power and those who don't. Marx and Engels suggests that studying history through the lens of dialectical materialism reveals that little has changed over time. The rich are able to enjoy realities from which the poor are closed. This element has remained the same over time. In terms of what has changed, Marx and Engels would be direct in suggesting that only the language has changed. The reality of economic oppression has not changed and while different terms might be applied, little else has changed. Dialectical materialism and the examination of the narrative in which there are people who have power and those who do not remains the same. This profound similarity underscores being in the world and subsumes any differences, which are cosmetic, at best. Marx and Engels would concludes that under a system where there is private ownership of wealth, little has really changed.
According to Marx in the first portion of the Communist Manifesto, entitled the the "Bourgeois and the Proletarians," all of history is characterized by struggles between various socioeconomic classes. The history of earlier eras, such as Rome and the Middle Ages, was driven by the interactions between individuals labeled as serf and lord, slave and freeman, and plebeian and patrician, whose interests and behaviors were in opposition to each other.
"In the earlier epochs of history, we find almost everywhere a complicated arrangement of society into various orders, a manifold gradation of social rank. In ancient Rome we have patricians,
knights, plebeians, slaves; in the Middle Ages, feudal lords, vassals, guild-masters, journeymen, apprentices, serfs; in almost all of these classes, again, subordinate gradations."
Modern society has "sprouted" from the legacies of the Roman Empire and the Middle Ages. While the linguistic references utilized to refer to these social classes have been altered by time, the opposition between those of high status and low status in society, have not. Marx also continues his tendency to characterize social classes in binaries.
"The modern bourgeois society that has sprouted from the ruins of feudal society has not done away with class antagonisms. It has but established new classes, new conditions of oppression, new forms of struggle in place of the old ones."
Marx labels these new classes that he is referring to as the Bourgeoisie and the Proletariat. Marx was also writing during the time of the industrial revolution when workers had few rights and became like the commodities that they were manufacturing. The introduction of industry into society had changed the conditions and struggles of workers (now the lowest class) into a new social landscape that differed from that of Rome and the Middle Ages.
In short, oppression of the lower classes of society remained that same; however, the conditions of oppression, struggles faced by the working class, and the term proletariat itself are new developments in Marx's dialectic model of history.