Schneier on Security

Bruce Schneier draws a parallel between modern security principles and the layered defensive architecture of Constantinople's Theodosian Land Walls. The walls featured four distinct defensive lines — a flooded moat, a low breastwork, an outer wall with 82 towers, and a massive inner wall with 96 offset towers — creating a nearly 30-meter barrier from moat bottom to tower top. The design exemplifies the 'defense in depth' concept, where multiple overlapping layers of protection maximize resilience against attackers.