Ecclesiastical independence did not preserve the Empire from political weakness. Phocas was soon seen to be worse than Maurice, and one conspiracy after another was begun in the Hippodrome and ended by a massacre in the streets. The Green faction in the Circus called the Emperor a drunkard and a madman to his face. Famine and pestilence ravaged the crowded city, and when Heraclius, already a renowned general, brought his fleet up the Hellespont and anchored at the Golden Horn the collapse of the power of Phocas was immediate, and a new Emperor was crowned in the great church of the "Capital of the World." The reign of Heraclius, gallant man though he was, began in almost unbroken disaster, and when in 615 Jerusalem fell into the hands of the Persians it seemed that the end was at hand. In the next year, as had already happened under Phocas, a Persian army encamped at Chalcedon. When negotiations were in vain, when Heraclius had even formed the idea of transferring the seat of Empire from Constantinople to Carthage, and had only abandoned it after his preparations were far advanced, when the terror and indignation of the people forced him to take oath before the patriarch in S. Sophia that he would never leave "the Queen of Cities," at length the courage of the empire awoke, the nobles sacrificed their wealth and the churches their treasures, the fleet utterly destroyed that of the Persians, and Heraclius delivered the city and the empire by a march as brilliant as it was daring. Leading five thousand veterans across Asia Minor and through the mountains he "penetrated into the heart of Persia and recalled the armies of the great king to the defence of their bleeding country." After three campaigns he returned in triumph and entered, as no Emperor since Theodosius the Great had done, by the Golden Gate.
In his absence thirty thousand Avars, who had swept over the Balkan provinces like a devouring flame, broke through the great wall and encamped under the very walls of the city itself. Churches in the suburbs were burnt to the ground and the famous Church of the Theotokos in Blachernae was on the point of being destroyed, when some panic caused the Avar horsemen to retire. The danger was too obvious for the warning to be neglected, and the Senate, which had refused with contumely the offers of the barbarian leaders, allies of the Persian King, drove back the enemy and immediately increased the fortifications by a new wall. This splendid barrier, magnificent to-day in its ruins, stretched from the enclosure outside the palace of Blachernae, at the foot of the sixth hill, to the Golden Horn. It is flanked by three hexagonal towers.