The peoples of the West have been trying to subjugate other countries for six centuries, relying on their technologies, but they do not always guarantee victory. Power over Nations explores the complex relationship between Western imperialism and new technologies. Why were the caravels and galleons that gave the Portuguese power over the Indian Ocean for a century unable to defeat the Muslim galleys in the Red Sea? Why did the weapons of the Spaniards, which crushed the Aztec and Mayan empires, not help them in Chile and Africa? Why did complete US air supremacy prevent the Americans from achieving their goals in Iraq and Afghanistan? Daniel Hedrick traces the evolution of Western technology and explains how environmental and social factors sometimes guaranteed victory and sometimes led to unexpected defeats. This book is a sweeping, fascinating and insightful history of technological progress, its promises, its limits, and the key role it played in the rise and fall of empires.