But the mind of Justinian was more occupied by foreign conquests than by commerce. Among his earliest maritime expeditions may be ranked the invasion of Africa and the overthrow of the Vandals, the preparations for which were not unworthy of the last contest between Rome and Carthage. Five hundred transports, navigated by twenty thousand mariners of Egypt, Cilicia, and Ionia, were collected in the harbour of Constantinople. If the smallest of these are computed at thirty, and the largest at five hundred tons, the average will supply an allowance liberal, if not profuse, of about one hundred thousand tons, for the reception of thirty-five thousand soldiers and sailors, and five thousand horses, with military stores and provisions sufficient for a three months’ voyage. When the fleet lay moored ready for sea before the gardens of the palace, the Patriarch, amid great pomp and solemnity, pronounced his benediction for its safety and success; and when the emperor had signified his last commands, the expedition, at the sound of a trumpet, got under way. It was attended with the most complete success. Carthage became subject to Justinian; and the Romans were again masters of the sea—a position they maintained until a more formidable power arose in the East, which declared war against the empire both by land and by sea. [Sidenote: Rise of the Muhammedan power, A.D. 622.] [Sidenote: A.D. 633.] It is not our province to trace the progress of that power, nor indeed of that of any nation, except as may be necessary to furnish an idea of the extent of its maritime commerce, so far as this can be ascertained from the limited sources of information now extant. Muhammed had not only introduced a new religion, but his warlike successors propagated their newly accepted faith by the sword with a success unparalleled in the history of the world. Nor were their exploits confined to the land. The Arabians, distinguished by the name of Saracens (that is, specifically “the _Easterns_”),[348] who, from the earliest period of history, were skilled as navigators, and daring as seamen, had by this time become not merely an important but a powerful maritime people. Masters of Persia and of the whole of the Arabian Gulf, the “true believers,” soon extended their conquests into Syria, nominally to abolish “infidelity,” but with a clear eye to the advantages of commerce. [Sidenote: Rapid conquests;] [Sidenote: of Jerusalem, A.D. 636;] [Sidenote: of Alexandria, A.D. 638;] [Sidenote: and of Africa, A.D. 647.]