In 1962, the US sent out a valid nuclear launch order with correct launch codes, by mistake.

https://www.vice.com/en/article/former-us-airman-tells-un-an... ("Former US Airman Tells UN an Accidental Nuclear War Was Narrowly Avoided in 1962")

https://news.ycombinator.com/item?id=10452983 ("The Okinawa missiles of October 1962 (thebulletin.org)", 71 comments)