Afew years ago over here, we had a problem with train doors flying open as they were going along when people leant on them.
Turned out that the firm overhauling/servicing them had squirted WD in 'em which had done as the advert claimed, and cleaned all the grease off of them, for a while the WD kept them lubed up but after a while the parts just dried up and the locks stuck, apparently.
Rather than start another thread just to ask this question I hope you don't mind if I slightly change the subject.
So it sounds like WD40 wasn't developed by the military,
but I did see a film where they used superglue to temporarily close a wound, claiming that it was developed by the US military for use in vietnam, with the hillarious line

"why do you think it sticks your fingers together so well"
I'm guessing that this is a pile of shite, but I know some of you guys overthere are in the military, any comments? thanks