Owing to the configuration of the ground traversed by the Mesoteichion, it was at this point that a besieging army generally delivered the chief attack. Here stood the gates opening upon the streets which commanded the hills of the city; here was the weakest part of the fortifications, the channel of the Lycus rendering a deep moat impossible, while the dip in the line of walls, as they descended and ascended the slopes of the valley, put the defenders below the level occupied by the besiegers. Here, then, for Constantinople was the “Valley of Decision”—here, in the armour of the city, the “heel of Achilles.”

In the siege of 626 by the Avars, the first siege which the Theodosian Walls sustained, the principal attack was made from twelve towers which the enemy built before the fortifications extending from the Gate of Charisius to the Gate of the Pempton, and thence to the Gate of St. Romanus.[[368]]

Upon the Gate of Charisius attempts were made: by Justinian II. and his allies for the recovery of his throne in 705;[[369]] by Alexius Branas against Isaac Angelus in 1185;[[370]] by John Cantacuzene in 1345[[371]] and through it the Comneni entered in 1081, by bribing the German guards (Nemitzi) at the gate, and wrested the sceptre from the hand of Nicephorus Botoniates.[[372]]

In 1206, during the struggle in which the Latins, soon after their capture of the city, involved themselves with Joannicus, King of Bulgaria, a raid was made upon the Gate of St. Romanus and the adjacent quarter by Bulgarian troops encamped near the capital.[[373]] In 1328 the gate was opened to admit Andronicus III. by two partisans, who stupefied the guards with drink, and then assisted a company of his soldiers to scale the walls with rope ladders.[[374]] In 1379 John VI. Palæologus and his son Manuel, after effecting their escape from the prison of Anemas, and making terms with Sultan Bajazet, entered the city by this gate, and obliged Andronicus IV. to retire from the throne he had usurped.[[375]]

But it was in the sieges of the city by the Turks that this portion of the walls was attacked most fiercely, as well as defended with the greatest heroism. Here in 1422 Sultan Murad brought cannon to bear, for the first time, upon the fortifications of Constantinople. His fire was directed mainly at an old half-ruined tower beside the Lycus; but the new weapon of warfare was still too weak to break Byzantine masonry, and seventy balls struck the tower without producing the slightest effect.[[376]]

In the siege of 1453 this portion of the walls was assailed by Sultan Mehemet himself with the bravest of his troops and his heaviest artillery, his tent being pitched, as already stated, about half a mile to the west of the Gate of St. Romanus.[[377]] At the Murus Bacchatareus fought the Emperor Constantine, with his 400 Genoese allies, under the command of the brave Guistiniani, who had come to perform prodigies of valour “per benefitio de la Christiantade et per honor del mundo.” The three brothers, Paul, Antony, and Troilus, defended the Myriandrion, “with the courage of Horatius Cocles.”

As the struggle proceeded two towers of the Inner Wall and a large portion of the Outer Wall were battered to pieces by the Turkish cannon. The enemy also succeeded in filling the moat at this point with earth and stones, to secure an unobstructed roadway into the city whenever a breach was effected.

On the other hand, Giustiniani repaired the breach in the Outer Wall by the erection of a palisade, covered in front with hides and strengthened on the rear by a rampart of stones, earth, branches, and herbage of every description, all welded together with mortar, and supported by an embankment of earth. Between this barricade and the Inner Wall he furthermore excavated a trench, to replace to some extent the moat which had been rendered useless; and to maintain his communications with the interior of the city he opened a postern in the great wall.

Against these extemporized defences assault after assault dashed in all its strength and fury, only to be hurled back and broken. Meanwhile, more and more of the Inner and Outer Walls fell under the Turkish fire, and the Sultan decided to make a general attack at daybreak on the 29th of May. The onset upon the Mesoteichion, directed by the Sultan in person, was, however, repeatedly repelled, and the day threatened to go against the assailants, when a Turkish missile struck Giustiniani and forced him to leave the field. His soldiers refused to continue the struggle, abandoned their post, and disheartened their Greek comrades. The Sultan, perceiving the change in the situation, roused his janissaries to make a supreme effort. They swept forward, carried the barricade, filled the trench behind it with corpses of the defenders, and passing over, poured into the doomed city through every available opening. Some made their way through the breach in the great wall, others entered by the postern which Giustiniani had opened,[[378]] while others cut a path through the heap of dead bodies which blocked the Gate of Charisius. The heroic emperor refused to survive his empire, and found death near the Gate of St. Romanus.[[379]] And through that gate, about midday, the Sultan entered, the master of the city of Constantine. It was the close of an epoch.

The next Theodosian gate stands between the last tower in the Outer Wall to the north of the Gate of Charisius and the old Byzantine Palace now called Tekfour Serai. In its present condition the entrance pierces only the Outer Wall; for the Inner Wall terminates abruptly a little to the south of the palace, having been broken away, probably when that edifice was erected. By way of compensation the Outer Wall was then raised higher and built thicker, and flanked by a large tower.