defense systems

OPPOSITE The Great Wall of China can be truly spectacular. Here we see an iconic stretch of the Ming Great Wall, constructed of fired brick, at Jinshanling in Hebei Province. This, though, is just one of the most celebrated stretches of an incredibly long and complex monument. ABOVE Great Walls. A map showing the course of the various Chinese walls. BELOW Remains of the Han Dynasty Great Wall, constructed of rammed earth, roughly 85km north west of Jiayuguan, Gansu Province. Comparing this to the Ming Great Wall at Jinshanling illustrates how varied the appearance of different stretches could be.

Long division: measuring the Chinese and Roman frontiers

What steps did the Chinese and the Romans take to control their empires? Peter J Brown and David J Breeze have been examining the extraordinary resources emperors were willing to expend in the name of security.