The Brits invented Sonar in 1916, and the Admiralty kept it secret for long enough that when World War 2 broke out, they had it fitted on 5 types of ships as part of an integrated anti-submarine suite; they were the only ones that had this operational capability.
If you were a scientist who worked on that project, and in 1920 you published "On Quartz-Based Range Detection In Water", you would have definitely gone to jail.
(Or, of course, the Enigma cracking -- but that's not really the best example; it wasn't a long-maintained operational advantage consisting of abilities the rest of the world didn't have, but rather an emergency skunk-works that got jump-started by the Poles; it did, however, have a pretty good record of secrecy after the fact!)
The Brits invented Sonar in 1916, and the Admiralty kept it secret for long enough that when World War 2 broke out, they had it fitted on 5 types of ships as part of an integrated anti-submarine suite; they were the only ones that had this operational capability.
If you were a scientist who worked on that project, and in 1920 you published "On Quartz-Based Range Detection In Water", you would have definitely gone to jail.
(Or, of course, the Enigma cracking -- but that's not really the best example; it wasn't a long-maintained operational advantage consisting of abilities the rest of the world didn't have, but rather an emergency skunk-works that got jump-started by the Poles; it did, however, have a pretty good record of secrecy after the fact!)