The history of warfare cannot be fully understood without considering the technology of killing, posits Paul Lockhart. For centuries, weaponry remained simple enough that any state could equip a respectable army, yet by 1870, the cost of investing in increasingly complicated technology soon meant that only a handful of great powers could afford to manufacture advanced weaponry, while other countries fell behind. Lockhart shows how armaments have transformed the very structure of power in the West, from the Renaissance to the dawn of the atomic era.