Baffled in his design to escape from his difficulties by flight, Heraclius took a desperate resolution. He would leave Constantinople to its fate, trust its safety to the protection afforded by its walls and by the strait which separated it from Asia, embark with such troops as he could collect, and carry the war into the enemy's country. The one advantage which he had over his adversary was his possession of an ample navy, and consequent command of the sea and power to strike his blows unexpectedly in different quarters. On making known his intention, it was not opposed, either by the people or by the Patriarch. He was allowed to coin the treasures of the various churches into money, to collect stores, enroll troops, and, on the Easter Monday of A.D. 622, to set forth on his expedition.
His fleet was steered southward, and, though forced to contend with adverse gales, made a speedy and successful voyage through the Propontis, the Hellespont, the Egean, and the Cilician Strait, to the Gulf of Issus, in the angle between Asia Minor and Syria. The position was well chosen, as one where attack was difficult, where numbers would give little advantage, and where consequently a small but resolute force might easily maintain itself against a greatly superior enemy. At the same time it was a post from which an advance might conveniently be made in several directions, and which menaced almost equally Asia Minor, Syria, and Armenia. Moreover, the level tract between the mountains and the sea was broad enough for the manoeuvres of such an army as Heraclius commanded, and allowed him to train his soldiers by exercises and sham fights to a familiarity with the sights and sounds and movements of a battle. He conjectured, rightly enough, that he would not long be left unmolested by the enemy. Shahr-Barz, the conqueror of Jerusalem and Egypt, was very soon sent against him; and, after various movements, which it is impossible to follow, a battle was fought between the two armies in the mountain country towards the Armenian frontier, in which the hero of a hundred fights was defeated and the Romans, for the first time since the death of Maurice, obtained a victory. After this, on the approach of winter, Heraclius, accompanied probably by a portion of his army, returned by sea to Constantinople.