Window
What was Window?
Window was a countermeasure used against German radar. It consisted of aluminium foil strips that were dropped from an Allied aircraft. The aluminium strips reflected the enemy radar creating a ‘cloud’ on their radar screen that hid the location of the Allied aircraft.
Lancaster dropping Window from bomb bay
Why was it so important?
German scientists were actively developing new radar systems with increasing effectiveness. Countermeasures to block/jam enemy radar were essential to avoid heavy losses. This gave rise to the expression “The Battle of the Beams”.
Where does the name come from?
The origin of the codename is not known.
A brief history of Window
Window was invented by Joan Curran (nee Strothers) who worked for TRE with her husband Sam. Window was developed in 1942, but was not used operationally until July 1943 due to fears that it might interfere with British radar systems, that it would fall into enemy hands, and because aluminium was in short supply. It was extremely effective, confusing enemy radar operators. Variants of his type of technology has continued to be used until the present day. It is now known as ‘chaff’.
Window was first employed in Operation Gomorrah, a series of raids on Hamburg, and resulted in a much lower loss rate than usual. Interestingly, as part of Operation Taxable on 5–6 June 1944, Window was dropped by Avro Lancasters of 617 Squadron to synthesize a phantom invasion force in the Straits of Dover and keep the Germans unsure as to whether the Allied assault would fall on Normandy or Calais.
[A biography of Joan Curran can be found in ‘People’ section of this website]
