It was an innovation - hazardous beyond doubt even in the view of its author - to which the untrustworthy character of the cavalry furnished by the subjects compelled him[34], that Caesar for the first time deviated from the old Roman system of never fighting with mercenaries, and incorporated in the cavalry hired foreigners, especially Germans. Another innovation was the appointment of adjutants of the legion (legati legionis). Hitherto the military tribunes, nominated partly by the burgesses, partly by the governor concerned, had led the legions in such a way that six of them were placed over each legion, and the command alternated among these; a single commandant of the legion was appointed by the general only as a temporary and extraordinary measure. In subsequent times on the other hand those colonels or adjutants of legions appear as a permanent and organic institution, and as nominated no longer by the governor whom they obey, but by the supreme command in Rome; both changes seem referable to Caesar's arrangements connected with the Gabinian law[35]. The reason for the introduction of this important intervening step in the military hierarchy must be sought partly in the necessity for a more energetic centralization of the command, partly in the felt want of capable superior officers, partly and chiefly in the design of providing a counterpoise to the governor by associating with him one or more colonels nominated by the Imperator.

The most essential change in the military system consisted in the institution of a permanent military head in the person of the Imperator, who, superseding the previous unmilitary and in every respect incapable governing corporation, united in his hands the whole control of the army, and thus converted it from a direction which for the most part was merely nominal into a real and energetic supreme command. We are not properly informed as to the position which this supreme command occupied towards the special commands hitherto omnipotent in their respective spheres. Probably the analogy of the relation subsisting between the praetor and the consul or the consul and the dictator served generally as a basis, so that, while the governor in his own right retained the supreme military authority in his province, the Imperator was entitled at any moment to take it away from him and assume it for himself or his delegates, and, while the authority of the governor was confined to the province, that of the Imperator, like the regal and the earlier consular authority, extended over the whole empire.

Moreover it is extremely probable that now the nomination of the officers, both the military tribunes and the centurions, so far as it had hitherto belonged to the governor[36], as well as the nomination of the new adjutants of the legion, passed directly into the hands of the Imperator; and in like manner even now the arrangement of the levies, the bestowal of leave of absence, and the more important criminal cases, may have been submitted to the judgment of the commander-in-chief. With this limitation of the powers of the governors and with the regulated control of the Imperator, there was no great room to apprehend in future either that the armies might be utterly disorganized or that they might be converted into retainers personally devoted to their respective officers.

But, however decidedly and urgently the circumstances pointed to military monarchy, and however distinctly Caesar took the supreme command exclusively for himself, he was nevertheless not at all inclined to establish his authority by means of, and on, the army. No doubt he deemed a standing army necessary for his state, but only because from its geographical position it required a comprehensive regulation of the frontiers and permanent frontier garrisons. Partly at earlier periods, partly during the recent civil war, he had worked at the tranquillizing of Spain, and had established strong positions for the defence of the frontier in Africa along the great desert, and in the north-west of the empire along the line of the Rhine. He occupied himself with similar plans for the regions on the Euphrates and on the Danube. Above all he designed an expedition against the Parthians, to avenge the day of Carrhae; he had destined three years for this war, and was resolved to settle accounts with these dangerous enemies once for all and not less cautiously than thoroughly. In like manner he had projected the scheme of attacking Burebistas king of the Getae, who was greatly extending his power on both sides of the Danube[37], and of protecting Italy in the north-east by border-districts similar to those which he had created for it in Gaul. On the other hand there is no evidence at all that Caesar contemplated like Alexander a career of victory extending indefinitely far; it is said indeed that he had intended to march from Parthia to the Caspian and from this to the Black Sea and then along its northern shores to the Danube, to annex to the empire all Scythia and Germany as far as the Northern Ocean - which according to the notions of that time was not so very distant from the Mediterranean - and to return home through Gaul; but no authority at all deserving of credit vouches for the existence of these fabulous projects. In the case of a state which, like the Roman state of Caesar, already included a mass of barbaric elements difficult to be controlled, and had still for centuries to come more than enough to do with their assimilation, such conquests, even granting their military practicability, would have been nothing but blunders far more brilliant and far worse than the Indian expedition of Alexander. Judging both from Caesar's conduct in Britain and Germany and from the conduct of those who became the heirs of his political ideas, it is in a high degree probable that Caesar with Scipio Aemilianus called on the gods not to increase the empire, but to preserve it, and that his schemes of conquest restricted themselves to a settlement of the frontier - measured, it is true, by his own great scale - which should secure the line of the Euphrates, and, instead of the fluctuating and militarily useless boundary of the empire on the north-east, should establish and render defensible the line of the Danube.

But, if it remains a mere probability that Caesar ought not to be designated a world-conqueror in the same sense as Alexander and Napoleon, it is quite certain that his design was not to rest his new monarchy primarily on the support of the army nor generally to place the military authority above the civil, but to incorporate it with, and as far as possible subordinate it to, the civil commonwealth. The invaluable pillars of a military state, those old and far-famed Gallic legions, were honourably dissolved just on account of the incompatibility of their esprit de corps with a civil commonwealth, and their glorious names were only perpetuated in newly-founded urban communities. The soldiers presented by Caesar with allotments of land on their discharge were not, like those of Sulla, settled together - as it were militarily - in colonies of their own, but, especially when they settled in Italy, were isolated as much as possible and scattered throughout the peninsula; it was only in the case of the portions of the Campanian land that remained for disposal, that an aggregation of the old soldiers of Caesar could not be avoided. Caesar sought to solve the difficult task of keeping the soldiers of a standing army within the spheres of civil life, partly by retaining the former arrangement which prescribed merely certain years of service, and not a service strictly constant, that is, uninterrupted by any discharge; partly by the already-mentioned shortening of the term of service, which occasioned a speedier change in the personal composition of the army; partly by the regular settlement of the soldiers who had served out their time as agricultural colonists; partly and principally by keeping the army aloof from Italy and generally from the proper seats of the civil and political life of the nation, and directing the soldier to the points, where according to the opinion of the great king he was alone, in his place - to the frontier stations, that he might ward off the extraneous foe.