In WW I Loomis worked for U.S. Army Ordnance and is credited with the inventions of the Aberdeen chronometer, a microscope centrifuge, and a pressurized fire extinguisher. It was said that Loomis was so brilliant that he could play entire games of chess in his head.

In the early 1920s Loomis had built a lab where he and his staff conducted experiments in sound waves, spectrometry and precise time measurements.

In the late 1930s he worked on a small microwave set in his spare time, it was mounted on a truck. The president's science advisor advised the president that he thought that all these civilian projects should be brought together under one roof. The National Defense Research Committee (NDRC), was created.

Vannevar Bush, President Roosevelt's Science Advisor and Alfred Loomis, contacted a scientist to test the jamming potential of proximity fuses that were being developed for the army by Dr. Merle Tuve. They wanted the fuses to be used but also wanted to access the potential for jamming them, since they were electronic. The scientist was to report back only to Loomis and Bush because they knew if the jamming was a success the fuses would never be used and they were too valuable a weapon. It seems the fuses were jamable and during the Battle of the Bulge in WW II the Germans had captured over 2000 of these shells. We build jammers to counteract them but the Germans never used the shells because their engineers stated that they would never work correctly, they were wrong.

In 1940 at Loomis's mansion at Tuxedo Park, New York there was a meeting of scientists. All were American except two physicists who came from Great Britain. A wooden box was produced by the British physicists that contained a cavity magnetron, this was a device that could generate one thousand times more power than any microwave transmitter known. It was presented to the American scientists. This was the keystone to a modern radar system. The British wanted our help in the war with Germany in return.

In 1940 the United States opened the MIT Radiation Laboratory for the development of radar systems. Alfred Loomis was the man in charge of the laboratory. The magnetron was the basis for these devices. The lab employed the top physicists in this country, ten of whom would win the Nobel Prize. Every kind of radar was developed here, surface to air, air to air and ship to ship, air to surface. While not actually inventing radar Loomis invented a scanning system for radar.

Loomis was fascinated with the idea of long range radio navigation. He worked on this idea and in 1942 the Loran system was born. It was used to pinpoint the location of attacking submarines.

Then a strange thing happened. In 1940 William Richards a Nobel Prize winner in Chemistry in 1915 was found dead with his wrists slashed. It seem he was about to publish a book about a Wall Street tycoon turned amateur scientist who had a private lab where murder had been committed. The title of the book was "Brain Waves and Death". The fictitious scientist was named Howard M. Ward but everybody knew it was really Alfred Loomis.

Loomis's cousin was Henry Stimson, Secretary of War under both Roosevelt and Taft and a very good friend of his was Ernest Lawrence, co-founder of Lawrence Livermore National Laboratory.