Quote:
Originally Posted by Harry Ree 
Window, which the Americans referred to as chaff was a secret passed to them after scientists in the British TRE had developed it to combat the German radar defences.It was the prime reason why the large raid on Hamburg on the night of 24/25 July 1943 was successful. It reduced RAF losses on the night to 1.5%.The Lufwaffe air defence system involving ground and air radar was severely disabled during this raid and was the first time that Window was used by the RAF. |
On the subject of window radar-blocking metallic strips, in mid-1942 this propaganda leaflet was printed on tin foil:
The hope was that disguising the foil as propaganda leaflets would help keep "window" a secret from the Germans. Following tests the metallic leaflets were found to successfully block radar and several thousand were printed as a result. But the deception wasn't considered a good one and it's not known if the leaflets were ever dropped on Germany. Surviving examples are very rare and the condition is generally poor as the ink did not adhere well to the metallic side of the leaflet.