Ambushing the enemy with weapons that stay undetected until their very strike can be an insidious, but efficient, military strategy. A team of weapons experts takes a look at three such inventions: the ancient Roman's caltrop, iron spikes spread across battlefields to bring horses and soldiers to their knees; the Dreyse needle gun, which changed the tactics of future armies; and the landmine, an age-old weapon lethally improved by modern technology.

用在攻击前不被发现的武器伏击敌人，可以是一种阴险但有效的军事战略。一个武器专家小组对三个这样的发明进行了考察：古罗马的卡尔特罗普，在战场上散布的铁钉使马匹和士兵跪地；德雷斯针枪，改变了未来军队的战术；以及地雷，一种通过现代技术进行致命改进的古老武器。