Sigint in Corregidor

Here's something I came across on how sigint was used in Corregidor and Bataan.

"Cryptoanalysis"
By an agreement between the US Army and the US Navy, reached at a conference in Manila in May 1941, the Navy's own Sigint unit, Cast, was to concentrate on breaking Japanese diplomatic traffic. For in the Navy Tunnel, Corregidor hid a secret copy of the Japanese Code Machine known as Purple - so ultra-secret and rare, even Pearl Harbour did not have one.


CRYPTOANALYSIS

 

Thanks for pointing out these sites.

 

Originally, Pearl Harbor was to have had a Japanese diplomatic code (Purple) machine, but they were all hand-built and there were very few of them available. PH's Purple machine instead went to the British who were supposed to trade a current German naval Enigma in return. This Enigma machine was never delivered to the US. Instead, the British substituted sketches and schematics of an Enigma machine. This was one of the reasons the US could not read the German U-boat codes for some time after entering hostilities against Germany.

MacArthur, who also had an Army SIS detachment in the Philippines, did not have much confidence in signals intelligence and seldom used the resulting information to his advantage. Later in the war, this changed and MacArthur's staff became adept at using sigint to plan future operations.