By Chris Wickham, Penguin, £25.
Though The Inheritance of Rome does not specifically focus on Christianity and the Latin Church, it does show how the religion and its institutions fit into the ancient world's military, social and political transformation as the empire broke up into Latin Christendom, Eastern Orthodoxy, and the Arab-Muslim world.
The Latin Church was the only western institution that remained more or less intact after the turbulent fifth century saw the end of the Roman Empire in the West.
This ending led to "economic simplification" and a fluid, even multicultural society where the Germanic peoples lived with the older Latin cultures. Perhaps one of the greatest changes was the aristocracy, which ceased to be a highly cultured class with villas and independent wealth. A militarised, largely Germanic land-holding nobility replaced the old Roman senatorial families.
Wickham shows how this social transformation affected the Church: the episcopacy by these centuries (500-1000) was almost exclusively from the aristocratic (that is to say, warrior) class. Bishops themselves warred if need be, and as able medieval administrators would take from the peasantry what they decided was theirs, regardless of Gospel teaching on serving the poor.
The Inheritance of Rome is most interesting in its discussion on Charlemagne and the wider Carolingian reformation of Church, society, and education. This dynasty, beginning with Charles Martel (717-41) and then the first duly crowned Carolingian king (in 751), Pippin, fused the institutional Church with the political administration. The episcopacy was appointed not by the pope but by the emperor or his officials. As literate, educated men, bishops helped administer the empire. In turn, Pippin did the Church a favour by introducing compulsory tithes, "which dramatically increased the wealth of the episcopal hierarchy everywhere in Francia", Wickham notes.
The author paints a realistic picture of the endemic violence of the era. Charlemagne wanted to take over Saxony, and steal the land from the peasantry to build a faithful aristocracy. This went along with one of the few instances of forced Christianisation in the period. Not surprisingly, the Saxons fiercely resisted both the political and religious takeover, but eventually lost.
Such violence notwithstanding, Charlemagne and his dynasty aimed to give moral, religious foundations to the empire with the help of the Church and Old Testament imagery.
This was truly revolutionary, as this moral undertone to society lasted for centuries. Education and morals went together for Charlemagne, so he encouraged a literary culture, which became the Carolingian Renaissance, led by Alcuin, Einhard and Paul the Deacon.
The ambitious, sweeping history contained in The Inheritance of Rome makes the reading sometimes less than fluid, as we jump around between England, Francia, the East and the Arabs.
Religiously inclined readers do get a sense of just how central Christianity and Islam were to the politics and society of the time. The Byzantine emperor, even with a succession of coups, fulfilled a religious duty as imperial leader and quasi-priest. Like his western peers he didn't hesitate to involve himself in theological disputes.
The religious re-ordering of society under the Arab-Muslim conquerors of North Africa, Spain and the Near East as far as the old Persian empire did not go as according to western propaganda.
Arabs did not force conversions by the sword. Except for a religious tax, life went on more or less as it did before the Muslim conquest, not least of all because in the earliest decades embracing the new religion necessitated adoption into an Arab tribe. Conversion was also discouraged because the local Arab military garrisons depended on the higher taxes levied on non-Muslims.
Wickham shows how society did alter: peasants converted to escape the tax, and merchants adopted Islam so that they could more easily deal with the Muslim governments.
Other changes did eventually occur, though they took more than a few decades: "Cities changed in structure. Their Roman monumental centres tended to fall out of use, as the Arabs had a different ceremonial style, with fewer religious or political processions and a focus on the enclosed public space of mosque courtyards."
The Great Mosque of Damascus, constructed between 705 and 716 by the Caliph al-Walid, was intended to show the local Greek-speaking Christian majority who the new city powers were. Yet conversion to Islam only became widespread in the ninth century. This gradual diminishment of Christianity in Muslim-controlled lands should not surprise the reader.
In the former Roman Empire, Christianity could not sustain itself without support from the top, Wickham clearly shows. In the West, the very health of the faith depended on political leadership. Monastic reform in western Europe in the 10th century, centred on Cluny, "was very heavily dependent on royal authority, and enhanced that authority in its turn".
Monasteries throughout this whole period in the West were family affairs, as important to aristocratic power as a castle was. It lent the family a moral status, and allowed it to control the land even after it had been granted to the monastery. The family bought spiritual capital - the prayer of the monks - for perpetuity in exchange.
As in the East, part of the mystique of the nobility was its Christian faith. The peasants, with their poorly educated priests (if the village had one at all) were an afterthought. Christianity and Islam were both highly political religions in this era, as indispensable to good royal government as the land and taxation were.