The art of fortification has existed ever since man first came to realize the value of natural obstacles to his common defense, and evolved as he sought to invoke his own methods to fully exploit that advantage. The building of barriers rapidly evolved from the simple mud parapets and mountaintop abodes of the Neolithic Age to the construction of linear and point stone obstacles of the Bronze Age, best represented by the Hittite capital of Hattusas. The Greco-Roman world was the proving ground for medieval fortifications. When Emperor Constantine I moved the capital of the Roman empire from Rome to the sleepy port town of Byzantium in AD 324, the opportunity to make full use of the state of the art in the construction of fortifications was at hand. The results of what followed shaped the course of world history.

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Located on a horn-shaped peninsula astride the Bosphorus and the Sea of Marmara, the renamed imperial capital of Constantinople dominated the narrow waterway that divides Europe from Asia. The complexities of that geography provided both advantages and challenges to the site’s defense. A steep and rugged shoreline and the Sea of Marmara’s swift currents protected the southern coast. To the north the Golden Horn, an inlet that bordered the peninsula, was a natural anchorage and harbor. The ancient Lycus River ran diagonally northwest to southeast across the peninsula, forming a narrow valley that sectioned the city into two distinct areas-a chain of six hills running along the Golden Horn to the north, and a single, larger hill to the south. A coherent urban defense had to address those considerations. For the most part, the many leaders and builders of the city succeeded in mastering the terrain. The ruins that still enclose what is now the Turkish capital of Istanbul are the remnants of centuries of evolution. Awe inspiring even in decay, they are a testament to the glory of Greco-Roman military art.

The despair of its enemies, the walls of Constantinople were the most famous of the medieval world, singular not only in scale, but in their construction and design, which integrated man-made defenses with natural obstacles. Their principal composition was mortared rubble, faced with blocks of fitted limestone and reinforced by courses of layered red brick. To enhance the integrity of the overall network, the towers and walls were built independently of one another. The entire city was enclosed in a defensive circuit of 14 miles of walls, reinforced by more than 400 towers and bastions, and several strong points and fortresses. The strongest construction faced west, against an approach by land. There, along a four-mile stretch of rolling land, stand the legendary Theodosian Walls, their depths blending together, the merlons overlapping like teeth in the mouth of an Olympian shark. There an enemy had to attack a linear obstacle of four belts, each ascending above the other, with a depth of some 200 feet.

The main line of defense was the Inner Wall, 40 feet in height and 15 feet thick, with a battlemented parapet five feet high that was accessed by stone ramps. Along its course at 175-foot intervals run 96 massive towers, each once capable of mounting the heaviest military engines of the day. A second, Outer Wall, approximately 30 feet high, is joined to this main wall by an elevated 60-foot terrace. The Outer Wall is also equipped with 96 bastions, each offset from the towers of the Inner Wall to avoid masking their fires. Subterranean passages run from many of those points back toward the city-avenues that presumably provided the defending troops with secure movement to and from a threatened area. From the Outer Wall extended another 60-foot terrace, ending in a 6-foot high parapet. This bordered a great moat, some 60 feet wide and 15 to 30 feet deep, supplied by an aqueduct system. To compensate for the rolling terrain, the moat was sectioned by a number of dams, which enabled it to retain an even distribution of water along its length. The five public gates that traversed the moat by way of drawbridges were set narrowly into the walls and were flanked by towers and bastions. Any assault made on the outer gates would be attacking into the strength of the defense. The belts were constructed at a tiered elevation, starting at 30 feet for the Inner Wall and descending to the moat. This, and the distance between strong points, ensured that an attacker, once within the network, was in range from all immediate points in the defense. The Land Walls were anchored at both extremities by two great fortresses. Along the Sea of Marmara, the Castle of the Seven Towers secured the southern approach, while in the north, along the Golden Horn, the salient that was the quarter of the Blachernae Palace, residence of the later Byzantine emperors, was gradually transformed into one massive fortress. To those two fortified points were adjoined the Sea Walls, similar in construction to the Outer Wall, of which little remains today.

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