Who does Marx say that the history of struggles is between? Give one specific example that he cites from The Communist Manifesto.

As Engels says in the 1883 preface to The Communist Manifesto,

all history has been a history of class struggles, of struggles between exploited and exploiting, between dominated and dominating classes at various stages of social evolution; that this struggle, however, has now reached a stage where the exploited and oppressed class (the proletariat) can no longer emancipate itself from the class which exploits and oppresses it (the bourgeoisie), without at the same time forever freeing the whole of society from exploitation, oppression, class struggles—this basic thought belongs solely and exclusively to Marx.

So class struggle—the struggle between those who labor day-by-day for a living and those who profit from the labor of others because they own the means of production—is the key struggle. This is important because other groups frame the conflict or struggle differently. The fascists, for example, see the universal struggle as not between economic classes, but between races. For example, the Nazis understood all the Aryan people, rich and poor, as united by race against common enemies such as Jews and Slavs. Nationalist ideologies in general understand people of one nation as united together against enemies comprised of an entire other country. For example, the US might say it is at war with "Iraq," not certain forces in Iraq that are hostile to its interests.

One specific example of struggle in The Communist Manifesto would be that of the artisan class, which Marx labels as part of the proletariat. The artisan class rebels against the factory mechanization of its work, which robs the artisan of his autonomy. He will initially fight back to smash the factory, trying to retain his freedom and not become a wage slave.

After industrialization, a group that Marx calls the lumpenproletariat forms: they are the doctors, lawyers and others who have lost prestige and power, who have been converted into wage earners, and some of them become reactionaries, wanting to return to a perceived golden age.