The course of affairs must have been widely different. As Darius allowed the bridge over the Bosphorus to remain, and left the fleet on the Danube, it cannot have been his fixed purpose to coast round the Black Sea. But in any case he must preserve his communications with Asia and Persia and support his army. All the sick, or wounded, or unserviceable men in the army, and all the messengers could only be sent back over the bridge on the Danube. The crews of the fleet were the rear-guard of the army, maintaining and defending its communications. It had also to provide for its own maintenance, _i.e._ for the needs of more than 100,000 men, and no doubt it likewise collected the provisions for the army by land. However great the stores which the army brought with it, they would soon be consumed in the steppe, unless supplemented. Wherever Darius marched, he could not venture, with the enormous mass of men and animals in his army, to go more than a few days' march at the most from the river-courses. The idea of retiring before the enemy naturally occurred to a people who were without a settled habitation, who wandered in hordes through fixed districts of pasture, living on the backs of their horses, and carrying their women and children with them in waggons drawn by oxen (III. 234). What had they to lose, and what could they fear from the Persians, if the unarmed, the women, children, servants, and herds, had already been sent at the right time under safe convoys far into the interior towards the neighbouring nations?--if all the men--and the Scoloti were not a numerous nation[271]--collected together, and accustomed as they were to abstinence, and living in continual movement, advancing far more lightly and rapidly on their steppe-horses than their encumbered opponents, hovered round their enemy, stopped up wells and destroyed pastures, without ever engaging in battle? If the Scythians were wise, they would not retire to the east, where Darius could approach the coast, and bring up his fleet with auxiliaries, but away from the sea, _i.e._ to the north. If the Scythians were not terrified by the enormous power of Darius, and knew how to avoid battles, the army of Darius would soon be ruined by its own numbers in the desert. As a fact this is the way in which the war beyond the Danube seems to have been carried on. Herodotus tells us that Darius came upon the Scythians three marches beyond the Danube. If he found their forces united, he must have hoped to engage them in a battle which would have decided the campaign at one stroke in his favour. But these mounted opponents could not be captured, Darius sinks deeper and deeper into the desert, till he is compelled by distress to return, and his retreat was made an occasion of heavy losses by the light-armed Scythians.