In an earlier post, I discussed the origins and nature of medieval serfdom. Here I discuss how it became less and less important, disappearing in some areas in the twelfth century.
Because serfs, "bound in the body," lived and worked next to free peasants--some of whom rented their land, some of whom owned their land outright--they always resented their status. The easiest way out was to "forget" that they were serfs. Because who was or wasn't a serf was rarely if ever recorded in writing, and because some of the things that really marked one's servile status (like restrictions on inheritance) came around only once a generation or so, serfs might be able quietly to pass for free. The danger was being called on it by one's peasant neighbors.
Or one could just run away. In an era without modern communication, no one would know where someone had gone, much less drag them back. "City air makes free," went an old proverb, because with the growth of twelfth-century towns serfs had a place to go where they could get a job and live, where everyone (serf and free peasant alike by origin) was an immigrant from the countryside.
In France in the early twelfth century, a number of peasants painstakingly saved up the money they were able to make from sale of produce and bought their way out of serfdom. A lord of the body would be quite happy to free a serf for twenty or thirty pennies, rather than getting one penny a year in head-tax. By the 1120s, serfdom was essentially gone from most of France.
The former serfs still owed their rents, the combination of labor dues and produce that they and their ancestors had always paid. But a number of lords became irritated at the difficulty of enforcing labor dues--workers grumbled about how far they had to come, tended to arrive late and leave early, and demanded lunch. These lords "commuted" a number of labor dues to cash payments, so that peasants paid an annual fee instead of working the lord's land, and the lord would then hire laborers who knew they would not get paid unless they worked hard.
This was fine with everyone, including young men trying to save up money to buy property or get married. That is, it worked until inflation set in, the inevitable result of a growing economy. Workers started demanding higher wages whereas the fees-in-lieu-of-labor were fixed in perpetuity. In the thirteenth century, landlords stopped commuting labor dues, and some even insisted that anyone who could be proven to have a servile ancestor had to come work for them. This was not as successful as they hoped.
In England, meanwhile, serfdom did not die out quite as quickly, in part because of the developing common-law courts. Only free men and women could sue or give evidence, and many a claimant won their case by arguing that their opponent was a serf and thus couldn't be in court at all. This made it much harder for people to quietly forget their servile origins.
In Germany, when knighthood began in the eleventh and twelfth centuries, the service knights (on whom see more here) were serfs, and indeed they continued to be serfs into the late Middle Ages. They lived and acted like aristocrats, even becoming governors of regions of eastern Europe, yet still legally kept their servile status. These "serf-knights" were known as ministeriales, those who served.
Although serfdom was at most a minor issue in the high and late Middle Ages in the west, it developed for the first time in Russia in the early modern period and persisted there until the nineteenth century.