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 New Commandership-in-Chief 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.
Caesar's Military Plans Defence of the Frontier 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.