The last great defensive work of the ancient world—and the first of
the medieval age—was built to protect the city of Constantinople. The
new Rome has been known by many names—Byzantion (the original
Greek port), Constantinople (Constantine’s city), or later Byzantium,
and today Istanbul. For his new capital city, Constantine selected a small
Greek port, Byzantion, on a peninsula. The sea and a sea wall protected
most of the city, but the land side of the peninsula required a heavier defensive
system. When the emperor Theodosius expanded the city early
in the fifth century, he ordered double walls and a moat for the vulnerable
side. The Theodosian walls stood as a model for medieval builders.
So effective were the walls that they protected the city until 1453 when
the Turks blasted through them using cannon.
Byzantine success depended on a system that combined vertical defense
with defense in depth, that is, high walls and towers with double
walls and a moat. The walls were built of stone and concrete and bonded
with layers of brick, creating a colorful banded effect. The great inner
wall was fifteen feet, six inches thick and had ninety-six towers, each of
which could become an independent fortress. No one was allowed to
build next to the wall; consequently, no traitor could bore through the
walls from the back of his house. The open space also permitted rapid
deployment of troops along the wall. Beyond the great wall, Theodosius’
engineers constructed a lower second wall about six feet, six inches thick;
men on the high inner wall could see and shoot over the heads of those
on the lower outer wall. A moat (water-filled ditch) defended the outer
wall from anyone attempting to tunnel under it or batter it down. The
moat was deep and wide and reinforced by low walls.
To review: an attacking army faced a triple line of defense. If they were
able to bridge the moat, they had to break through a wall, only to be
trapped in front of an even stronger wall overlooked by fortress-towers.
Such elaborate defenses required the vast resources of an empire to build.
No western prince could afford the materials and the crew of skilled masons
necessary to replicate the walls of Constantinople. Not until the
twelfth century did such complex defensive structures appear in the West.
World History
