The navy, active and efficient in the loth century, is described by a military and therefore unprejudiced officer of the 11th as the glory of Romania. But towards the end of the z ith century it declined, the main cause being the disorganization of the naval provinces of Asia Minor, which, as we saw, was a result of the Seljuk conquest of the interior. This decline had important indi rect consequences; it led to the dependence of the empire on the Venetian navy in the struggle with the Norman power, and for this help Venice exacted commercial privileges which injured Byzantine commerce and opened the door to the preponderant influences of the Venetians in eastern trade. In the period of the Palaeologi the imperial navy, though small, was active; and the importance which it possessed for the State is illustrated by the high rank at court which the admiral (who in the Iith century had received the title of great duke, Soti) then occupied; the only minister who was superior to him was the great domestic.
Diplomacy.—In protecting the State against the barbarians who surrounded it, diplomacy was a weapon as important in the eyes of the Byzantine Government as soldiers or fortifications. The peace on the frontiers was maintained not only by strong mili tary defences, but by more or less skilful management of the fron tier peoples. In the later empire this kind of diplomacy, which we may define as the science of managing the barbarians, was prac tised as a fine art ; its full development was due to Justinian. Its methods fall under three general heads. (r) One people was kept in check by means of another. The imperial Government fo mented rivalry and hatred among them. Thus Justinian kept the Gepidae in check by the Lombards, the Kuturgurs by the Utigurs, the Huns by the Avars. (2) Subsidies were given to the peoples on the frontiers, in return for which they undertook to defend the frontier adjacent to them, and to supply fighting men when called upon to do so. The chiefs received honours and decorations. Thus the Berber chiefs on the African border received a staff of silver, encrusted with gold, a silver diadem, white cloak, embroidered tunic, etc. More important potentates were invested with a cost lier dress. In these investitures precedence was carefully observed. The chiefs thus received a definite position in the empire, and the rich robes, with the ceremony, appealed to their vanity. In some cases they were admitted to posts in the official hierarchy,—being created patricians, masters of soldiers, etc. They were extremely fond of such honours, and considered themselves half-Romans. Another mode of winning influence was to marry barbarian princes to Roman wives, and rear their sons in the luxury of the palace.
Dissatisfied pretenders, defeated candidates for kingship, were wel comed at Constantinople. Thus there were generally some princes, thoroughly under Byzantine influence, who at a favourable oppor tunity could be imposed on their compatriots. Throughout Jus tinian's reign there was a constant influx of foreign potentates to Constantinople, and he overwhelmed them with attentions, pom pous ceremonies and valuable presents. (3) Both these methods were already familiar to the Roman Government, although Justin ian employed them far more extensively and systematically than any of his predecessors. The third method was new and character istic. The close connection of religion and politics at Constanti nople prepares us to find that Christian propaganda should go hand-in-hand with conquest, and that the missionary should co-op erate with the soldier. The missionary proved an excellent agent. The typical procedure is as follows. In the land which he under takes to convert, the missionary endeavours to gain the confidence of the king and influential persons, and makes it a special object to enlist the sympathies of the women. If the king hesitates, it is suggested that he should visit New Rome. The attraction of this idea is irresistible, and when he comes to the capital, the pomp of his reception, the honours shown him by the emperor, and the splendour of the religious ceremonies overcome his last scruples. Thenceforward imperial influence is predominant in his dominion; priests become his advisers ; a bishop is consecrated, dependent on the patriarch of Constantinople; and the barbarians are trans formed by the penetration of Byzantine ideas. By the application of these various means, Justinian established Roman influence in Nubia, Ethiopia and south Arabia, in the Caucasian regions, and on the coast of the Euxine. The conversion of the Lazi (of Col chis) was specially notable, and that of the Sabiri, who were politi cally important because they commanded the eastern pass of the Caucasus known as the Caspian Gates. It will be observed that the great prestige of the empire was one of the conditions of the success of this policy.
The policy had, of course, its dangers, and was severely criti cized by one of Justinian's contemporaries, the historian Pro copius. Concessions encouraged greater demands; the riches of the empire were revealed. It was a system, of course, which could not be permanently successful without military power behind it, and of course it was not infallible ; but in principle it was well f ounded, and proved of immeasurable value.