CHAPTER XII. THE WALL OF THE EMPEROR HERACLIUS: THE WALL OF THE EMPEROR LEO THE ARMENIAN. The fortifications extending from the north-western angle of the enclosure around the Palace of Blachernæ to the Golden Horn consist of two parallel lines, connected by transverse walls, so as to form a citadel beside the Golden Horn. The inner wall belongs to the reign of Heraclius; the outer is an erection of Leo V., the Armenian. The Heraclian Wall was constructed in 627, under the following circumstances:—[555] Until that year the quarter of Blachernæ, at the foot of the Sixth Hill, was a suburb immediately outside the fortifications.[556] The fact that the suburb and its celebrated Church of the Theotokos, containing, it was believed, the girdle of the Blessed Virgin, were thus exposed to the attacks of an enemy did not occasion serious concern. In the opinion of the devout citizens of Constantinople, the shrine, so far from needing protection, formed one of the strongest bulwarks of the capital. At the worst, when danger threatened, the treasures of the sanctuary could be readily transported into the city, as was done in the reign of Justinian the Great.[557] But in 627, Constantinople learned what a siege really meant. Persia and the Empire were then at war with each other; and while Heraclius was carrying the campaign into the enemy’s country, a Persian army had encamped at Chalcedon for the purpose of joining the Avars in laying siege to the capital.[558] As the Byzantine fleet, however, commanded the Bosporus, the allies could not unite their forces, and the Avars were left to act alone. The undertaking proved too difficult for the barbarians, notwithstanding the vigour with which it was conducted, and the siege was raised. But before retiring, a troop of Avaric horse set itself to devastate the suburbs, and having fired the Church of SS. Cosmas and Damianus, and the Church of St. Nicholas, dashed into the open ground beside the Church of Blachernæ, intent upon devoting also that sacred edifice to the flames. For some reason, that purpose was not carried into effect, and the church escaped all injury. This marvellous deliverance enhanced, indeed, the reputation of the Theotokos, but it likewise aroused a sense of the danger to which her shrine was liable, and so the Government of the day ordered the immediate erection of a wall along the western side of the Blachernæ quarter, to place the church beyond the reach of hostile attack in future. The wall was known, until the erection of the Wall of Leo, as the Single Wall of Blachernæ (Μονοτείχος Βλαχερνῶν:[559] τεῖχος τῶν Βλαχερνῶν).[560]