From From Peoples into Nations: A History of Eastern Europe, by John Connelly (Princeton University Press, 2020), Kindle pp. 270-271):
For Marxists then and later, nationality was a secondary form of identity: nations rose with capitalism and would disappear when capitalism gave way to socialism. And even while they existed, nations had no value as such; nationhood was ephemeral and unsubstantial, not a lasting site of human identity.
Still, Marx and Engels were not non-national; they were culturally German and despised the small peoples who hindered the consolidation of large, “historical” nations like France, Germany, and Italy. Marx ridiculed the idea that the insignificant Czechs, living at the heart of a dynamic Germany, could have a separate state, and Engels wrote that in every corner of Europe, one encountered the “ruins” of peoples, ready to side with reaction against “historical” peoples with their missions to humankind: Scots against English, Bretons against French, Basques against Spaniards, and most recently and tragically, the “barbarian” Czechs and South Slavs against Germans and Hungarians. But Engels had not lost faith. “The next world war,” he wrote in January 1849, “will cause not only reactionary classes and dynasties, but also entire reactionary peoples, to disappear from the face of the earth. And that is also progress.”
As Engels aged, his fury tempered, but he never abandoned the notion that small peoples were “relics.” It was misguided, he wrote in 1866, to think that the “Roumans of Wallachia, who never had a history, nor the energy required to have one, are of equal importance to the Italians who have a history of 2,000 years.” The national movement continued to grow among Czechs, but he still considered them a nuisance, destined to be “absorbed as integral portions into one or the other of those more powerful nations whose greater vitality enabled them to overcome greater obstacles.” Other “remnants of bygone Slavonian peoples” that he mentioned as destined to fade into greater peoples were the Serbs, Croats, Ukrainians, and Slovaks.
The disdain for small peoples extended beyond Marx and Engels to the German socialist elite, to Ferdinand Lassalle, Johann Baptist von Schweitzer, Johann Phillip Becker, Wilhelm Liebknecht, and the left liberal Leopold Sonnemann. Liebknecht, co-founder of the Social Democratic Party of Germany (SPD), considered the workers’ movement an “infallible tool to eliminate the nationalities question.” If humans saw their interests in material terms, in their ability to produce wealth and be properly rewarded, who cared what language they spoke? The imperial states were not racist and provided opportunities for Czechs or Poles who rose through education in the state bureaucracies as long as they used the imperial language. If one’s interest was universal culture, why not just use German or Russian? Socialists found no justification in history for the heart of the East European nationalist project: rescuing local vernaculars from the edge of extinction.