Bushi military training differed from era to era. During the late medieval period, the "Age of the Country at War," military training for most bushi was not all that elaborate. Most warriors, especially rank-and-file bushi and ashigaru, probably learned just the basics of weapons handling from their fathers and/or their peers, and then acquired most of their skills through experience and practice--kind of the way American inner-city kids learn to street-fight today. Some took this sort of thing more seriously than others and went looking for teachers or had access to real bugei experts nearby--or passing through. Most didn't need or seek out extensive formal instruction. There were, of course, a handful of men who really dedicated themselves to perfecting the arts of blade-to-blade combat, but the fact that so many ryu trace themselves to the same people strongly suggests that this wasn't all that widespread a phenomenon. There are a few dozen really famous martial artists from the late 15th and 16th centuries, and there probably weren't more than a few hundred teachers around at any given time, even in medieval times.

During the Tokugawa era, when bugei ryu evolved into the kind of organizations we know today, the vast majority of bushi probably did little or no training. Tokugawa bushi were sword-bearing bureaucrats mostly, not sword-wielding warriors--because there were no wars. In fact, it's likely that the total number of real experts, and possibly even the total number of serious students, in the bugei wasn't significantly higher in Tokugawa Japan than it is today.

Please don't confuse ryu with "clans." The tie-in between the two isn't direct.

Most medieval and Tokugawa era daimyo had personal bugei teachers for themselves and their families, and these teachers all belonged to one ryu or another. But the same ryu could and did provide this sort of teacher for more than one daimyo. And daimyo could and did employ teachers from more than one ryu. Many daimyo, especially during the Tokugawa era, also operated domain schools staffed by teachers from one or more ryu for their bushi retainers. Policies as to who could, or must, attend this sort of instruction varied from domain to domain and daimyo to daimyo. Of course, there were also a great many ryu that were entirely or almost entirely localized in a single domain. Many domains had several of these, including some, like the Kunii house's Kashima-Shin-ryu, that were purely family traditions. Other ryu were more national in scope, headquartered in major cities like Edo or Kyoto and offering instruction to bushi from numerous domains. (This was why bugei schools became focal points of the anti-Shogunate movements during the late 1800s: they were places where bushi from different domains could legally meet and interact, without immediately drawing the suspicions of domain and shogunal officials.) The word "clan," in reference to a political or military organizations of medieval and Tokugawa era daimyo, is one that should be thrown out. The guys who write the subtitles for bushi movies seem to love it, but it's a lousy word for describing what Japanese warlords headed up. Daimyo did make use of familial-sounding terms and titles for their subordinates, but daimyo armies and polities weren't really built around kinship ties. "Domain" is the word most historians use for these things.

The following was written by Dr. Friday in response to a question about clans and bugei training prompted by what he wrote.

"Clan" has basically zero relevance to warrior history, and little meaning at all in Japanese history after the 8th century or so. The main familial unit for warriors and non-warriors alike was the household. Kinship ties, both real and fictitious, were exploited in various ways by would-be warlords attempting to establish "feudal" (for lack of a better word) control over large areas of lands and peoples, but the bonds that were formed were actually based on financial and military dependency, not kinship. What late medieval and early modern bushi controlled were essentially autonomous countries (in medieval times) and semi-autonomous satrapies (in Tokugawa times). "Domain" is the term most historians writing in English use to refer to these entities. In both the early modern and medieval eras, these domains could be defined by geographic boundaries, but in the Sengoku period they were really defined as the sum of the lands held by the lord and his vassals, whose lands were in turn defined by those held by them and their vassals, and so on down the line. This meant that domain shapes were fluid and contingent on vassal loyalty, which was highly fluid and contingent, until warlords began to find ways to change this, in the late 1500s and beyond."