The previous chapter ended with the re-established Roman empire of western and central Europe having to learn how to cope with the prolonged attacks of Scandinavian sea-borne assailants, while the eastern Roman empire had recovered from its own darkest days to be able to confront more effectively than for many centuries the power of the Muslim rulers of the Middle East and North Africa. During the period comprising (roughly speaking) the ninth to eleventh centuries of the Christian era, a number of new features developed that make a study of military technology and engineering particularly fascinating. These included the appearance in the Byzantine empire of a number of treatises that provide evidence of what Byzantine commanders were expected to do. The historical accounts suggest that the texts were not abstract ideals, but offered practical guidance largely followed by the generations of successful generals who flourished particularly in the tenth century. Contemporary evidence also supports the case that in the world of the caliphs (a title to which there were three simultaneous claimants by the end of the tenth century), despite political turmoil, the wealth of the rulers contributed to continuity in the level of theoretical and practical knowledge and technical skill on which military rulers could draw.

The empire established by Charlemagne was sub-divided into what would become France (ruled by Charles the Bald, 840–77) and Germany (ruled by Louis the German, 840–75), either side of a “middle kingdom” (under Lothair, who inherited the title of emperor, 840–55) originally stretching from the North Sea to Provence and encompassing northern and central Italy (subsequently divided again, with the northern parts absorbed by their eastern and western neighbours thirty years later). The Carolingian dynasties reigning in all of these territories gave way to new families, the Capetians from 987 in “France” and the Saxon dynasty from 919 in “Germany”. There were simultaneously major social changes, most rapid in “France” but spreading everywhere in time, commonly associated with the term “feudalism”.

One element of these new regimes was the disappearance of central authority: those who had formerly served Charlemagne as royal local officials (the counts) established their own dynasties and in turn created followings of local land-holders, who were sometimes only theoretically but sometimes also practically obliged to serve them.