I've been thinking about sketching out some rules for running a campaign that has reach the natural end-game of D&D. Taking a point from Delta's "Realism in Game Design" and Cariadoc of the Bow's adage that the medievals usually knew what they were doing better than we do, my thoughts naturally turned to researching the the units actually cited in the historical record.
Arable and in England was traditionally divided into units known as hides, each notionally capable of supporting one peasant household. The actual physical size of each hide varied depending on the quality of the land, but it is generally assumed to be about 120 medieval acres, or 30-40 modern ones, pretty close to the American “forty” or ⅟₁₆ section (usually ⅟₁₆ square mile, depending on whether in was next to a township boundary where the convergence of lines of latitude made a difference). After the conquest, these were generally grouped into knight’s fees, the fief required to support a single knight with his household, horses, and equipment. The amount has been cited variously as between 2 and 27 hides and most typically at 5. We may assume that in practice an “average” manor, like that shown in Shepherd’s Historical Atlas, had about 10 such households, equivalent to an Anglo-Saxon tithing, plus a varying amount of additional forest, wooded parkland, wasteland, water, etc. A “typical” small barony might have the duty of supplying a group of ten knights, known as a constabularia, to the baron’s liege lord, roughly corresponding in size to an Anglo-Saxon hundred (literally, 100 households, grouped for administrative purposes), and thus consist of ten manors averaging out to this size. Baronies around the time of the conquest ranged in duty, from being required to supply about half of a constabularia to several such units. With even a small two-league hex being about 31 square miles, many such baronies could fit within a single hex on most campaign maps.
The knight’s service, the basic unit on which this is founded, involves supplying one man equipped with lance, mail, shield, helm, and warhorse to fight for up to 40 days each year when called to war (close to the previously mentioned half-season). Usually, this was done by granting a manor (known as a knight’s fee) to a knight in return for such service, along with additional duties guarding his lords castle, etc., but it could also be done by hiring a mercenary free lance (hence, freelancer) on the occasion of service, running about ₤20 in 1200 CE, or more commonly expressed as 30 marks (nota bene: for convenience, the mark used in Heathen's Heartbreaker, for now, is a variant mark of 120d rather than 160d). Later, as the use of mercenaries and the cash economy became more common this money would be paid directly to the king, a tax know as scutage. Beyond such formal vassalage, each freeman (perhaps 10% of the population, more in towns and cities) was required to keep at least a spear, gambeson, and iron cap, and so a manor might expect to bring as many or more footmen to war as it did knights, and each knight was likely to bring a substantial retinue of their own.
Most manors were run on the open field system, in which the manor’s land was divided between planted and fallow land, and the land to be planted was divided into narrow strips, with peasant households assigned to strips scattered about the manor, about ⅔ their own, with the rest going to the manor’s lord (known as his demense, which would also include various parks or waste) and the local church (the glebe).
The height of agricultural technology of the time was three-field crop rotation system, in which ⅓ of fields were used to grow winter wheat or winter rye, planted in early winter (September to December) and harvested in early autumn (August, hence Bread Feast or Lammas), another ⅓ used for crops planted in early spring and harvested in late autumn, such as oats, barley, peas, legumes, or fiber crops such as flax or hemp, and the last ⅓ was left fallow and often used for pasture (which further restored the land by providing manure). Earlier than the high medieval period a two-field system was in place, but it would likely be less than the naive estimate of two-thirds less productive than the three-field system of crop rotation, by virtue of the more advanced technique growing a more diverse set of crops, some of which had a further positive influence on the condition of the soil. Similarly, the later four-field system, cycling winter-grain, spring-grain, turnips, and clover over four years, is likely more than one-third more productive than the three-field system, as the crop diversity further increases and the fallow period is replaced by one of fodder production, which indirectly increases the production of human food. It would not be unreasonable to estimate a doubling of productivity with each technological advancement (if not more).
Manors of this sort might be thought of as fairly typical, but in practice they varied in almost every possible detail. Other arrangements of similar scale could also fit well into a similar structure, given a varying economy of scale implied by the agricultural technology available.. For instance, an Anglo-Saxon hundred-reeve would have similar judicial and tax duties over the same area and people as such a Baron (in fact, these institutions often existed side-by-side in England), but prior to the conquest would have ruled over free men that owned their lands and was obligated to a lead a larger number of less well-equipped foot soldiers to to fight in the fyrd instead of providing knights. On the other hand, a Roman latifunda might cultivate a similar area, but with the workers being slaves owned outright by a master rather than nominally free serfs, with military service performed by member’s of the owner’s immediate family. A later period knight, whose title was in name only and implied no actual military role, might rule over a larger number of peasants that work the land more productively and simply pay a tax to the king for the support of his armies and clerks.
This leaves lots of significant questions to answer. How much income should a baseline barony provide, in terms of crops, corvee labor, and ready coin? What could a barony's worth of corvee labor be expected to build each year, and how much would it cost to hire more? What could a lord to expect to make from a resource such as a forest of bee-trees, a flock of sheep, a small lead mine, or a toll bridge? One of the most important relates to the length of time to make a "turn" for such high level play; I've got some thoughts on that for another post.