Ultimately, this mounting class conflict [in the 13th to 15th centuries] brought about a new alliance between the bourgeoisie and the nobility, without which proletarian revolts may not have been defeated. It is difficult, in fact, to accept the claim, often made by historians, according to which these struggles had no chance of success due to the narrowness of their political horizons and the "confused nature of their demands." In reality, the objectives of the peasants and artisans were quite transparent. They demanded that "every man should have as much as another" (Pirenne 1937: 202) and, in order to achieve this goal, they joined with all those "who had nothing to lose," acting in concert, in different regions, not afraid to confront the well-trained armies of the nobility, despite their lack of military skills.
If they were defeated, it was because all the forces of feudal power--the nobility, the Church, and the bourgeoisie--moved against them, united, despite their traditional divisions, by their fear of proletarian rebellion. Indeed, the image that has been handed down to us, of a bourgeoisie perennially at war with the nobility, and carrying on its banners the call for equality and democracy, is a distortion. By the late Middle Ages, wherever we turn, from Tuscany to England the the Low Countries, we find the bourgeoisie already allied with the nobility in the suppression of the lower classes. For in the peasants and the democratic weavers and cobblers of its cities, the bourgeoisie recognized an enemy far more dangerous than the nobility--one that made it worthwhile for the burghers even to sacrifice their cherished political autonomy. Thus, it was the urban bourgeoisie, after two centuries of struggles waged in order to gain full sovereignty within the walls of its communes, who reinstituted the power of the nobility, by voluntarily submitting to the rule of the Prince, the first step on the road to the absolute state.
[Citation references Henri Pirenne's Economic and Social History of Medieval Europe.]