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. It will be remembered that in the year 575 Baduarius, the son-in-law of the emperor, had appeared in Italy at the head of an army, had been beaten by the Lombards, and a little later had died, probably in 575.[1] This man was not only a great Byzantine official, but the destined successor of Justin and one of the first personages of the empire. It is obvious, if at such a moment he commanded the imperial armies in Italy, he was supreme governor of the province And it seems certain that it was to mark the amalgamation in him of the two offices, military and civil, that the new title of exarch was created.[2] [Footnote 1: Migne, lxxii. 865; Joannes Biclarensis, _s.a_. 575; cf. Hodgkin, _op. cit_. v. p. 195, and Diehl, _u.s_.] [Footnote 2: "It is only an hypothesis," says M. Charles Diehl, the originator of this theory, "but it explains how, between the prefect Longinus (569-572) and the exarch Smaragdus (584) was produced in the years 572-576 the administrative transformation out of which rose the exarchate."]