If the previous boundary of the empire ran from the middle Danube up to its source and to the upper Rhine, and thence down that river, it was, at all events, materially shortened and improved by being shifted to the Elbe, which in its head-waters approaches the middle Danube, and to its course throughout; in which case, probably, besides the evident military gain, there came into view also the political consideration that the keeping of the great commands as far as possible remote from Rome and Italy was one of the leading maxims of the Augustan policy, and an army of the Elbe would hardly have played such a part in the further development of Rome as the armies of the Rhine but too soon undertook. The preliminary conditions to this end, the overthrow of the Germanic patriot-party and of the Suebian king in Bohemia, were no easy tasks; nevertheless they had already once stood on the verge of succeeding, and with a right conduct of the war these results could not fail to be reached. But it was another question whether, after the institution of the Elbe frontier, the troops could be withdrawn from the intervening region; this question had been raised in a very serious way for the Roman government by the Dalmato-Pannonian war. If the mere impending movement of the Roman Danube-army into Bohemia had called forth a popular rising in Illyricum, that was only put down by the exertion of all their military resources after a four years' conflict, this wide region might not be left to itself either at the time or for many years to come. Similar, doubtless, was the state of the case on the Rhine. The Roman public was wont, indeed, to boast that the state held all Gaul in subjection by means of the garrison at Lyons 1200 strong; but the government could not forget that the two great armies on the Rhine not merely warded off the Germans, but also had a very material bearing on the Gallic cantons that were not at all distinguished by submissiveness. Stationed on the Weser or even on the Elbe, they would not have rendered this service in equal measure; and to keep both the Rhine and the Elbe occupied was beyond their power. [Sidenote: And its abandonment.]