Revolution in military affairs (sometimes called RMA) is when a country's military uses new technology or new ways of fighting to get ahead of their enemies. For example, during World War II, the Germans used something called 'Blitzkrieg', where they used fast tanks and planes to quickly take over cities. That was a revolution in military affairs because no one had used fast tanks and planes in a war before. RMA can also help a country win wars more quickly and with less damage to people and things.