It is interesting that FM was overlooked and the US military wanted to remain on the unreliable AM. In this YouTube video, it sets out the history of FM adoption by the US military during world war 2…
How One Radio Engineer’s ‘ILLEGAL’ Frequency Hack Gave Infantry 3-Mile Range
None of this is my work, it was a very entertaining and interesting piece of FM history by the WWII Rising Stories channel.
More information on Wikipedia…