"About the year 626, the Persians, Avars, and Slavs came with a great host and besieged the imperial city of Constantinople while the Emperor Heraclius and the main body of the Byzantine army were absent in the East. Enemy ships filled the sea, especially the Golden Horn, and on land the adversaries were ready for attack with foot-soldiers, horses, and engines of war. Though the citizens courageously withstood them, yet they were few in number and would be unable to repulse the attack of such a great host. Hence, they could not count on any other means of salvation, except the protection of the Theotokos. And truly, suddenly a violent tempest broke up all the ships and submerged them, and the bodies of the invaders were cast out near the Blachernae quarter of the city where the famous Church of the Theotokos stood. Taking courage from this, the people went forth from the city and repulsed the remaining forces, who fled out of fear. In 673, the city was miraculously delivered yet again, this time from an invasion of the Arabs. Then in 717-718, led by the Saracen general Maslamah, the Arab fleet laid siege once more to the city. The numerical superiority of the enemy was so overwhelming that the fall of the Imperial City seemed imminent. But then the Mother of God, together with a multitude of the angelic hosts, appeared suddenly over the city walls. The enemy forces, struck with terror and thrown into a panic at this apparition, fled in disarray. Soon after this, the Arab fleet was utterly destroyed by a terrible storm in the Aegean Sea on the eve of the Annunciation, March 24, 718. Thenceforth, a special "feast of victory and of thanksgiving" was dedicated to celebrate and commemorate these benefactions. In this magnificent service, the Akathist Hymn is prominent and holds the place of honour. It appears that even before the occasion of the enemy assaults mentioned above, the Akathist Hymn was already in use as the prescribed Service for the Feast of the Annunciation, together with the kontakion, "When the bodiless one learned the secret command," which has the Annunciation as its theme. It was only on the occasion of the great miracle wrought for the Christian populace of the Imperial City on the eve of the Annunciation in 718 that the hymn "To thee, the Champion Leader" was composed, most likely by Saint Germanus, Patriarch of Constantinople.
Historians have ascribed the Akathist Hymn to Patriarch Sergius of Constantinople (638), to Saint George the Confessor, Bishop of Pisidia (818), or even to Saint Photius the Great (891), all of whom lived either at the time of or after the above-mentioned sieges. However, it appears most likely from its language, content, and style that the true composer of the Akathist Hymn is Saint Romanus the Melodist (6th century)."
Holy Monastery Dionysiou - Panagia of the Salutations the Myrrhgusher