Throughout history, military leaders have sought new ways to obtain military advantages when major changes in the nature of warfare threatened to upset the status quo. Napoleon was at the forefront of harnessing the power of a people-in-arms, using rising nationalism to create enormous armies that swept through Europe. Grant fought the American Civil War using much-improved technology that made obsolete everything he had learned about military tactics and strategy. Eisenhower managed a war effort between competing allies that involved major technological changes, including the emergence of atomic weapons. In the past 15 years, the administrations of George W. Bush and Barack Obama have been quick to field the latest military technology from drones to cyber war. This lecture narrated the history of “revolutions in military affairs” and the lessons for today.