I’m pretty sure it’s systematic agriculture
The daily life of a serf was hard. The Medieval serfs did not receive their land as a free gift; for the use of it they owed certain duties to their master. These took chiefly the form of personal services. Medieval Serfs had to labor on the lord's domain for two or three days each week, and at specially busy seasons, such as ploughing and harvesting, Serfs had to do do extra work. The daily life of a serf was dictated by the requirements of the lord of the manor. At least half his time was usually demanded by the lord. Serfs also had to make certain payments, either in money or more often in grain, honey, eggs, or other produce. When Serfs ground the wheat he was obliged to use the lord's mill, and pay the customary charge. In theory the lord could tax his serfs as heavily and make them work as hard as he pleased, but the fear of losing his tenants doubtless in most cases prevented him from imposing too great burdens on the daily life of the serf.
The Pentagon Papers "revealed that government officials had misled Congress and the American people about the war," since it was argued that President Johnson knew far more about the detailed horrors and failed strategies of the war than he let on.
