Covering the period from the earliest conquests in Syria and Iraq to the reduction of the caliphate to a purely symbolic rôle (ie. the 630s to the 930s), Kennedy tries to follow the organizational, social, technological, and tactical evolution of caliphal armies. Note that this largely excludes not only irregular rebels like Kharijites or the Qarmatians, but also the armies of the various breakaway dynasties that eventually escaped the caliphs' political control - towards the end of the period caliphal control was restricted to parts of Iraq and western Iran.

The book presumes a working knowledge of the political history of the period: well-known, and indeed, to most of us, little-known, events and individuals are frequently mentioned cursorily en route to some illuminating incident without being explained or introduced. It can probably be safely assumed that anyone considering a book like this already knows who Harun al-Rashid was, but the same doesn't apply, in my case at least, to al-Hajjaj or Babak. There's a brief glossary of Arabic terms employed; something similar for the more important people mentioned would've been appreciated.

That said, I liked it enough I find myself wishing for a similar book, if one can be written, on the abovementioned Kharijite and Qarmatian rebels. Alas, I suspect the sources simply aren't there for a similar work.