curprev12:5612:56, 1 February 2020 Aradirtalkcontribs m117,390 bytes+21 "Ultra" was the british intelligence, primarily regarding germany. "Magic" was the american codename for japanese decryption. I guess the british also decrypted some japanese codes, but here it seems MacArthur gets it before the australians, so most likely from an american, not a british sourceundo