On medieval battlefields, soldiers sought protection from enemy attacks by wearing heavy armour. Today, modern composite materials such as Kevlar can absorb the impact of lethal projectiles fired from small arms.
Thick bunker walls made of reinforced concrete are intended to protect individuals from larger projectiles. Such defensive systems are often developed in response to new offensive technologies. The culmination of this escalation is the nuclear bomb – the most radical manifestation of humanity waging war against itself.