I was reading an account of the behind-the-scenes science efforts during World War II and ran across a description of the bizarre “standoff” of sorts between the British and Germans concerning the use of chaff as an anti-radar countermeasure.
By 1942, the British had a working chaff system that involved using strips of aluminum to confuse aircraft tracking radar. But the British had a bit of a conundrum. If they started equipping their aircraft with chaff, the aluminum strips would inevitably be recovered by the Germans who would be able to fairly quickly reverse engineer it and then use it in their own aircraft.
So the British had to decide if the ability to enhance their offensive capabilities over German-controlled airspace was worth possibly enhancing the German offensive capabilities of British-controlled airspace. Ultimately, they decided not to deploy their chaff system in 1942 because of fears of Germany launching a new Blitz over Great Britain.
Here’s where the weird standoff comes in. The Germans had independently invented their own chaff system which was also tested and could have been deployed in 1942. But their military reached the same conclusion as the British — if they deployed the chaff system, the British would be able to reverse engineer it fairly quickly and deploy it themselves. Germany, like Great Britain, decided that enhancing their own offensive air capabilities was not worth the potential blowback of enhancing the Allies’ offensive air capabilities.
This odd situation exited until July 1943 when the British decided to deploy their chaff systems after developing new radar technology that they believed would allow them to target German aircraft even if the Germans began deploying the chaff system themselves.
(Wikipedia has a nice account of this situation in its entry on chaff countermeasures).