Defense in Depth, Medieval Style

This article on the walls of Constantinople is fascinating.

The system comprised four defensive lines arranged in formidable layers:

The brick-lined ditch, divided by bulkheads and often flooded, 15-20 meters wide and up to 7 meters deep.
A low breastwork, about 2 meters high, enabling defenders to fire freely from behind.
The outer wall, 8 meters tall and 2.8 meters thick, with 82 projecting towers.
The main wall—a towering 12 meters high and 5 meters thick—with 96 massive towers offset from those of the outer wall for maximum coverage.

Behind the walls lay broad terraces: the parateichion, 18 meters wide, ideal for repelling enemies who crossed the moat, and the peribolos, 15–20 meters wide between the inner and outer walls. From the moat’s bottom to the highest tower top, the defences reached nearly 30 meters—a nearly unscalable barrier of stone and ingenuity.

Tags: defense, history of security, physical security

Posted on April 15, 2026 at 6:47 AM • 6 Comments

Comments

AlexT • April 15, 2026 7:03 AM

Eventually defeated 🙄

Winter • April 15, 2026 7:18 AM

@AlexT

Eventually defeated 🙄

Literally only defeated after 1000 years. And then they were defeated at great costs by using guns which were invented long after it was designed and build.

I would sign up to defenses that will keep up for 1000 years.

Clive Robinson • April 15, 2026 9:48 AM

@ Winter, AlexT, ALL,

Sun Tzu observed [1], that is two simple rules,

1, Never attack the enemy when they have the high ground and supplies.

2, Never get in the enemies way when they are descending from the high ground. Let them waste energy and supplies by doing so.

Having the high ground is what these defences are in effect all about, as well as making an attackers only route of attack harder than even attacking uphill.

Modern military thinking has just reworded these ideas, and defined new battle spaces.

Hence we’ve got in modern battle space terms,

1, High Ground.
2, Air superiority.
3, Space superiority.
4, Cis-Luna superiority.

As time goes on these battle spaces will enlarge.

Consider being up in the region of space where rocks of large mass float around in Solar orbit. It takes very little effort to cause them to head down toward earth via the “gravity gradient” by which time their potential energy has converted to very large kinetic energy that is greater than many nuclear weapons…

[1] A modern translation is,

“He who occupies high Yang ground :
And ensures his line of supplies
Will fight to advantage.

On precipitous terrain :
If you occupy it first,
Yo should hold the Yang heights and wait for the enemy.

If the enemy occupies it first, do not go after him,
But entice him out by retreating.”

lurker • April 15, 2026 1:39 PM

And for fantasy Liu Cixin had it circumvented in 1453 by a bubble of four dimensional space drifting past. Most reviews ignore this opening chapter “real world” illustration of a significant plot device used later in the narrative.

https://en.wikipedia.org/wiki/Death%27s_End

Jon • April 15, 2026 2:00 PM

See also Bret Deveraux on ‘Fortifications’.

https://acoup.blog/2021/12/10/collections-fortification-part-iii-castling/

Long articles in a five-part series – still def. worth reading. Part III has (near the end) details and diagrams of the Theodisian walls.

(And, as pointed out above, resisted for a thousand years until the invention of cannon that could successfully blow holes in it).

The Historical • April 16, 2026 12:30 AM

Turkish history is a lie because Turks adopted their culture from Kurds. In many historical books, Turkish people are described as barbarians.