-Proximity Radio Fuse

https://commons.wikimedia.org/wiki/File:MK53_fuze.jpg

Officials of the War and Navy Departments rank this fuse, along with radar and the atomic bomb as one of the three outstanding scientific contributions to World War II. This fuse allowed for proximity triggered detonations making more effective anti-aircraft artillery and bombs. The existence of this fuse and the technology behind it were kept secret by the Allies to maintain a strategic advantage.