Gibbon Chapter XLIX: Iconoclasm, Charlemagne and the Holy Roman Empire
This chapter has three parts: first, the growth of the controversy about the use of icons in religious worship, and how this drove a wedge between the Pope and the Empire; second, the rise of Charlemagne and the re-foundation of the Western Empire; and third, the subsequent re-foundation of the Holy Roman Empire and a brief sketch of its history, finishing by contrasting the Holy Roman Emperor Charles IV, at his coronation in 1356, with Augustus, who started it all. I must say I found it a really enlightening chapter; I had had no idea that it was iconoclasm that made possible the rise of the Carolingians and brought an end to the Byzantine presence in Italy. (Is that still the received scholarly wisdom?)
See also my reflections on Gibbon's anti-Catholicism, Pope Joan, and scholars and gentlemen.