The outbreak of this war, which was fraught with such momentous consequences to the whole course of civilisation, found the Empire strangely divided. The Emperor of Italy and Africa was allied with the Emperor of Egypt, Syria, and Asia Minor, against the rulers of the armies of the Danube and the Rhine. We shall see that the alliance was—at any rate, in result—defensive rather than offensive. Licinius and Maximin never moved; they simply neutralised one another, though the advantage clearly lay with Constantine and Licinius, for Maxentius was absolutely isolated, so far as receiving help on the landward side was concerned. We need not look far to find the real cause of quarrel between Constantine and Maxentius, whatever pretexts were assigned. Maxentius would never have risked his Empire for the sake of a father whom he detested; nor would Constantine have jeopardised his throne in order to avenge an insult. Each aspired to rule over the entire West; neither would acquiesce in the pretensions of the other. Both had been actively preparing for a struggle which became inevitable when neither took any radical steps to avoid it. We have already seen that Constantine kept the larger part of the army of Gaul stationed in the south near Arelate and Lugdunum, in order to watch the Alpine passes; we shall find that Maxentius had also posted his main armies in the north of Italy from Susa on the one side, where he was threatened by Constantine, to Venice on the other, where he was on guard against Licinius. There is a curious reference in one of the authorities to a plan formed by Maxentius of invading Gaul through Rhaetia,—no doubt because Constantine had made the Alpine passes practically unassailable,—while Lactantius tells us that he had drawn every available man from Africa to swell his armies in Italy.