Development of the cavity magnetron during World War II helped change the destiny of Allied forces as high frequency radar with enough power to detect distant targets while being out of the easy detection bands of Axis forces' receivers. It was considered a top-level secret with great concern that the technology not fall into the hands of German and Japanese scientists. According to this early post-war advertisement in Radio News, Bell Labs was totally consumed by the development of magnetrons, and was relieved to finally be able to boast of its critical role now that the war was over.
Here is an interesting paper titled, "The Cavity Magnetron in World War II: Was the Secrecy Justified?"
Bell Telephone Laboratories Ad
Victory Reveals a Mystery
More than two years ago, an engineer of the Laboratories visited U.S.S. Boise, returned with a mysterious box which went into the Laboratories' vault. Now, victory opens the box and discloses a special kind of electron tube called a magnetron. It was part of a Radar which furnished data to aim U.S.S. Boise's guns during the night action off Savo Island on October 11-12, 1942. Because of the high frequency generated by this magnetron, the Radar was not detected by the enemy and the action was a complete surprise. Six Japanese warships were sent to the bottom of the sea.
This magnetron is a symbol of the Laboratories' enormous war program. Half of it was devoted to Radar, the other half gave birth to radio transmitters and receivers, sonar apparatus for the Navy, loudspeaker systems for ships and beach-heads, fire-control apparatus for anti-aircraft artillery. Coming months will unfold the story of these and many other contributions of the Laboratories to the victory of our arms.
Bell Telephone Laboratories' war work began before the war; until now, it claimed practically all our attention. With victory, we will go back to our regular job - helping to bring you the world's finest telephone service.
Bell Telephone Laboratories
Exploring and inventing, devising and perfecting, for continued improvements and economies in telephone service.
Printed in U. S. A.
Posted November 1, 2015