The Rad Lab's origins trace to a desperate gamble by Winston Churchill. By the summer of 1940, Britain was fighting for survival and needed American industrial muscle. Churchill authorized the Tizard Mission, a secret delegation that carried a black metal box across the Atlantic containing Britain's most closely guarded military technologies. Among them was the cavity magnetron, a device that could generate powerful microwave pulses -- the key to building radar sets compact enough to fit on aircraft and precise enough to track individual ships or aircraft. American physicist Alfred Lee Loomis, a millionaire who ran his own private laboratory, recognized the magnetron's potential immediately. He arranged funding through the National Defense Research Committee. MIT was chosen as the site, and Caltech physicist Lee A. DuBridge was recruited to direct the operation. The first researchers arrived in October 1940. Within months, the Rad Lab had outgrown the British efforts that had been running for years.

The Rad Lab's home was Building 20, a hastily erected wooden structure on MIT's campus that was supposed to be temporary. It lasted until 1998. The building's flimsy construction turned out to be an asset: researchers drilled holes through walls, strung cables across ceilings, and reconfigured spaces at will without worrying about damaging anything permanent. This physical flexibility fostered the intellectual kind. Physicists, engineers, and military officers worked side by side in an atmosphere that prized results over hierarchy. The lab's organizational genius was DuBridge, who structured research into focused divisions -- each targeting a specific radar application -- while encouraging constant cross-pollination. By 1943, the Rad Lab was delivering a stream of increasingly sophisticated devices. The SCR-584 became the finest gun-laying radar of the war, capable of tracking aircraft with enough precision to direct anti-aircraft fire automatically. The SCR-720 gave Allied night fighters the ability to find and destroy enemy bombers in total darkness, becoming the standard airborne interception radar for both American and British forces.

The Rad Lab's inventions altered the course of battles on every front. Their H2X radar, an American improvement on the British H2S system, allowed bombers to identify targets through cloud cover by mapping the terrain below using microwave reflections. The system operated in the X band at shorter wavelengths, giving sharper resolution than anything previously available. On the seas, Rad Lab microwave radar broke the back of the German U-boat campaign: submarine commanders who had hunted with impunity in the Atlantic darkness suddenly found themselves illuminated by radar they could not detect. The lab also developed Loran-A, the first worldwide radio navigation system, originally known as LRN for Loomis Radio Navigation. Loran allowed ships and aircraft to determine their position with unprecedented accuracy over vast oceanic distances, transforming naval logistics and transoceanic flight. By the war's end, the lab had produced $1.5 billion worth of radar systems -- roughly $26 billion in today's dollars -- and its work was credited as a decisive factor in Allied victory.

The Rad Lab was more than a weapons factory -- it was a crucible for twentieth-century science. Ten future Nobel Prize winners worked there, including I.I. Rabi, who served as associate director, and Luis Alvarez, who developed ground-controlled approach radar for landing aircraft in zero visibility. The lab's 28-volume Radiation Laboratory Series, published by McGraw-Hill after the war, became the definitive reference for microwave engineering and remained essential reading for decades. When the Rad Lab closed on December 31, 1945, its functions scattered: some went to industry, some to other MIT departments, and in 1951 the newly formed MIT Lincoln Laboratory inherited much of its defense-related mission. The Research Laboratory of Electronics, still active at MIT today, traces its lineage directly to the Rad Lab. The wartime lesson -- that concentrated scientific talent, given clear objectives and adequate funding, could produce transformative results at astonishing speed -- shaped American science policy for the rest of the century.

Building 20 was demolished in 1998 to make way for the Frank Gehry-designed Stata Center, which now occupies the site. There is no grand monument to the Rad Lab on MIT's campus, just as there was no grand announcement of its existence during the war. The lab's work was classified for years, and even after declassification, radar never captured the public imagination the way the atomic bomb did. Yet many military historians argue that radar contributed more to Allied victory than any other single technology. It was radar that won the Battle of Britain, radar that defeated the U-boats, radar that allowed bombers to find their targets and fighters to find their prey. All of it flowed through a wooden building in Cambridge where four thousand people worked in deliberate obscurity, hidden behind a name designed to sound as uninteresting as possible.