Again: his caution is seen in the fact that, after descending the Alps with the Army of Reserve, he immediately took measures to concentrate his forces, instead of crossing the Po at Chivasso and of marching directly to the relief of Masséna. He knew that a great battle was inevitable, yet safety was his first object. He wished to gain a position where he could bring a strong force on to the battle-field, and where, if defeated, he could retreat without losing his army. In fact, throughout the campaign, he kept a watchful eye upon his communications. It was his rear that gave him the greatest anxiety. It is always so with the great masters of war. "While the distant spectator," says Hamley, "imagines a general to be intent only on striking or parrying a blow, he probably directs a hundred glances, a hundred anxious thoughts, to the communications in his rear, for one that he bestows on his adversary's front." Notwithstanding the fact that Napoleon seemed always to take great chances in his military career, and seemed often to stake everything on the fate of a single battle, yet a careful analysis of his campaigns shows that no commander has ever looked with more anxiety to his lines of retreat than did this great master of war. At Austerlitz, where he allowed the enemy to envelop his right and cut off his retreat on Vienna, and where he was so certain of success that he issued a proclamation in advance explaining the manoeuvre by which victory would be obtained, yet even here he had provided for a retreat through Bohemia in case of defeat. This campaign was indeed a bold one; but it must be remembered that the very boldness of Bonaparte was one of the principal causes of his success. By descending the Alps into Italy upon the Austrian rear, he surprised his adversary and caused him to tremble for his communications. By this means he struck terror into the heart of Melas even before a battle had been fought. No sooner had French troops reached the valley of the Po than Melas was compelled to change his whole plan of campaign. He had then to defend himself against Bonaparte. He could no longer think of invading France. By this bold movement Bonaparte snatched the initiative from his adversary and compelled him to fight on the defensive. In war, the boldest course is often the safest. "The greatest soldiers have always been the most daring."