This really caught my attention and i thought that it must have been a translation error and i looked for the manifesto in German ( i was reading it in Spanish) and the word that appears is "Ritter" which as far as i understand only means "knight". What am i missing? Marx surely would have been familiarized With medieval knights due to their popularity during the romantic era so I'm really puzzled by this possible mistake.
Pd: In case you were wondering, Yes, I was casually reading the communist manifesto
/u/Commustar is correct in noting that these are the equites, although by the time the equites can be called a "class"--what Cicero calls to as the ordo equester--they no longer had really anything to do with the public or private horse. However, something to note is that while Marx's argument that political conflict throughout history has been class conflict has been extremely influential not just in political philosophy but also on historians, who use Marxist theory as the basis for doing things like social history, Marx's actual understanding of historical class conflict is notoriously lacking