If Darius’s real object was to extend his empire, or take revenge upon the Scythians, his failure was complete and humiliating; if undertaken on the ground suggested by Atossa as a measure of policy, a safety–valve to guard against the explosion of Persian turbulence, his purpose probably was fully answered in the loss and suffering which the army underwent. But whatever were his motives, he escaped more easily and creditably than most generals who have presumed to contest the possession of their deserts with the numerous and active cavalry of Tartary and Persia. Troops of the highest character, irresistible where their proper arms and discipline can be made available, have often sunk under the fatigue and hardships of warfare against a new enemy, under a new sky, and have been conquered by circumstances, almost without the use of the sword. By varying the climate and natural features of the earth—by giving man a frame which, notwithstanding the wonderful flexibility which adapts it equally for the snows of Greenland and the vertical splendour of the torrid zone, is ill calculated for violent and sudden changes, Providence has set bounds in some degree to the march of ambition, and often turned the triumph of the conqueror into mourning. We shall devote the rest of this chapter to relating a few of the most striking disasters which have occurred from the neglect of these considerations, and the rash invasion of regions where the elements, the face of the country, or the manners of its inhabitants have presented invincible obstacles to the success of the attacking army.