[Footnote 1:  For what follows cf.  Diehl, Etudes sur l’administration Byzantine dans l’Exarchat de Ravenne (1888).]

The transformation out of which the exarchate arose was slow and obscure, not the work of a great creative mind, but of necessity.  It was the result of many causes which it is not difficult to name; they were the progress of the Lombard conquest, the condition imposed upon the unconquered parts of Italy by that conquest, and especially the new necessity for defence imposed on the imperial power.

It is obvious that the result of the first ten years of that conquest was a complete destruction of the limits of the old Roman provinces of Italy.  A new grouping of territories was not only necessary but was already forming itself under the pressure of the conquest and its terror.  The regions which had escaped the barbarians were drawing together without any regard for the ancient provincial divisions and were grouping themselves about the cities, where the resistance, such as it was, was concentrating itself, and where the imperial administration had taken refuge.

If we confine ourselves for the moment to Italy north of the Apennines, we shall find that in the old province of Liguria the vicar of the prefect of the praetorium had fled from Milan to Genoa, and that about that city the debris of the old province was slowly re-assembling itself.  In Venetia we shall find that the governor had departed to Grado, and about this town as a centre the eastern part of the old province was gathered.  The western part of that province, cut off from its capital, attached itself by force of circumstances to what remained of Aemilia and of Flaminia, whose neighbour she was, and these fragments of the ancient provinces all together grouped themselves about, or found their centre in, Ravenna, the capital of Flaminia and the residence of the prefect of Italy.

In these new groupings the great pre-occupation and the supreme interest are defence—­the defence of civilisation against the barbarian.

Now, it was to regulate this new state of affairs that the exarchate was created; or rather the exarchate was the official acknowledgment of a state of affairs that the disastrous invasion of the Lombards had brought about.  The new order was established at the end of the reign of Justin II. (565-578) under a new and supreme official.  Without doing away with the prefect of Italy the emperor placed over him as supreme head of the new administration the exarch[1] who was both the military commander-in-chief and the governor-general of Italy; and, since the chief need of Italy was defence, without entirely suppressing the civil administration, he placed at the head of each of the re-organised provinces a certain military officer—­the duke.

[Footnote 1:  For the discussion of the derivation of the title “Exarch,” see Diehl, op. cit. pp. 15-16.]

The earliest document that remains to us in which we find definite mention of the exarch is the famous letter, dated October 4, 584, of pope Pelagius II. to the deacon Gregory, his nuncio in Constantinople.  It is probable that the exarch at this time was Smaragdus, but it is extremely improbable that he was the first to bear the new title.  This it would seem was a much nobler and more notable person.