In 1940, a team of British scientists arrived in Washington bearing Britain's most closely guarded technological secrets - including the cavity magnetron, a revolutionary new source of microwave energy. Its arrival triggered the most dramatic mobilization of science in history, as America's top scientists enlisted to convert the invention into a potent military weapon. Microwave radars eventually helped destroy Japanese warships and Nazi buzz bombs, and enabled Allied bombers to see through cloud cover. After the war, the work of the radar veterans continues to affect our lives - controlling air traffic, forecasting the weather and providing physicians with powerful diagnostic tools. With anecdotes and revelations, this work explores the work of the scientists who created a winning weapon and changed the world forever.