Battle of Sebennytos (641)

Following the crucial events after the battle of Heliopolis in 640, and the subsequent siege and capture of the fortress of Babylon by Rashidun forces, the Prefect of Egypt, Theodore, evacuated his remaining forces overnight to the neighboring island of Rauda, following a brief five-day ceasefire for Easter. The survivors of the onslaught at Babylon fortress soon abandoned the site on Easter Monday and began a demoralized retreat northward through the Nile Delta, towards Nikiû and Alexandria. After invseting the fortress of Babylon and the remaining troops within it, Amr immediately set about securing the surroundings of Egypt. Initially a Rashidun attack on the fortress of Misr failed, but soon thereafter the strength of Amr's forces was further bolstered by Egyptian turncoats, who provided him ships to transport his men across the Nile. These also assisted him in constructing two bridges across the rive. One bridge was built north of Babylon fortress to prevent Byzantine ships from reinforcing the fortress, while the other was raised at the eastern branch of the Nile, at Qalyub. Amr marched across the latter bridge and captured the towns of Menouf and Athrib. Amr sought to press his advantage further by dividing his army into two columns, sending the second force southwards to suppress isolated Byzantine resistance and secure agricultural supply lines, while leading the main contingent north to pursue Theodore’s column along the waterways before the Byzantines could reorganize, advancing from Athrib towards Sebennytos.^[3][4]

By this time, the Emperor Heraclius had dispatched reinforcements to Egypt under Marianos the Eunuch, which partially offset the losses sustained by Theodore during the disaster at Heliopolis. To slow the Arab advance down, Theodore dispatched two local garrison commanders to establish a brief rearguard line near the town of Sebennytos, using both regular Byzantine troops and Egyptian militiamen. However, upon witnessing the speed and ferocity of the approaching Muslim scouting parties, the militia raised from the native men of the area refused to cooperate with the Byzantine high command to oppose the Rashidun army. Nevertheless, the professional Byzantine troops in the area were in sufficiently high spirits to oppose the Muslims without the support of the locals. At this time, the terrain surrounding Sebennytos had been flooded by overflowing waterways, thus producing marshland, which negated the Rashidun advantages in tactical manoeuvrability. In particular, the presence of moats and canals in the area nullified the advantages usually held by the swift-moving Rashidun mounted troops. Leveraging the terrain as a force multiplier, the Byzantine troops were able to frustrate the efforts of the Amr's army to dislodge them, thus handing a rare but limited defeat to the Rashiduns. Unable to break through the Byzantine lines to take Sebennytos, Amr was forced to retreat, having sustained significant losses in the fighting.^[5][2]

Following the defeat, Amr withdrew to the town of Busir. As he feared the prospect of Theodore exploiting the Byzantine victory to launch an offensive against the Muslim forces, Amr took the precaution of fortifying this location. The nearby forts of Menouf and Athrib were also repaired and garrisoned. However, Theodore did not attempt to follow up the success gained by his men, allowing Amr to return to Babylon fortress and intensify his siege of the fortress, eventually facilitating its capture by the Arabs.^[b][8]