This is not a narrative history in the sense of a chronicle of emperors and wars, or even of Byzantine military organization and its relationship with the rest of society, but within its basically thematic approach, there is a strong emphasis on historical evolution, on what changed and what remained constant.

A lot of attention is paid to what you might call the ideological superstructure of Byzantine warfare, in particular how they squared their pacific Christian ideals with pragmatic necessity of defending the empire against an imposing array of enemies, and on the differences in attitude between the Constantinopolitan elite and the emerging Anatolian aristocracy. (What local elites in the rest of the empire thought seems to be less well known - and for a good chunk of the period there wasn't much of a rest of the empire anyway.)

Haldon credits the rise of said aristocracy with a major role in the disintegration of the Byzantine "system" in the 11-12th centuries; he also stresses the rise of the Latin West which left the Byzantines bereft of their old organizational superiority on that front. Perhaps surprisingly, he seems to see the Turks, who did the dirty work of conquering the empire's Anatolian heartland from the late 11th century on, as more a symptom than a cause. In favour of this interpretation note that Anatolia had previously been overrun by Persians in the 7th century and repeatedly by the Arabs in the 7-9th centuries without fatally weakening the empire or managing to permanently occupy it; what was different was, perhaps, less the nature of the invaders than the ability of the Byzantines to weather the storm.

Other chapters deal with standard mil-hist topics like organization, logistics, equipment and tactics. Haldon seems most at home, however, when discussing the military's relationship with the state and society in general.

The start date of the subtitle is far more precise than the text justifies - Haldon frequently refers to developments all the way back to the third century, but the book primarly deals with the period after the initial Arab conquests in the 630s and 640s - whereas the 1204 end date is observed pretty consistently, and little is said about Byzantine armies after the Fourth Crusade beyond that they relied heavily on mercenaries.

Happy enough about the book overall, I might have liked more on tactics and less on ideology, but I basically got what I expected and what the back cover promised.