The Great Valdarian Revolts were a series of peasant rebellions against the aristocracy of Valdar in the early 200s. The revolts caused a definite end to the aristocracy and ushered in the modern Republic of Valdar.
The first signs of dissent was just after the monarchy was dissolved, and nobles took over the running of the country in was sort of a loose federation, divvying up portions of the country for their own ruling, and warring with each other, cutting off trade and cooperation with what used to be neighboring villages. This dissent boiled into open rebellion following the one thing the populace hates the most, increased taxes. This first started when tax collectors were beat and hung by angry peasants, and escalated into armed conflict when troops descended into villages because of fears from the nobles of rebellion.
While the peasants were highly outmatched by the trained soldiers, they were numerous, and most of the drafted soldiers didn't care to fight people they knew, sometimes family. Deserting rates were high, along with soldiers simply refusing to fight. Also present was the sheer amount of towns, villages, and hamlets revolting. While armies would put down one revolt, two more would spring up. Villagers refused to help soldiers in any way, even going so far as to work against them.
When this series of revolts threatened to spiral into full-on guerilla warfare, the nobles relented, releasing their iron grip on the nation and began peace talks with well-known peasant leaders. While the nobility had certainly taken the loss, the peasants weren't really in any shape to reach for far-reaching goals, such as the dissolution of the caste system or whatnot. In the end, the talks ended in the founding of Valdar as a republic, and the lessening of the power of the nobles. This event disturbed the caste system, but it didn't cause it's demise, that would be up to the Valdarian Diplomatic Incident of 548.