At Bletchley Park he worked on the cryptanalysis of Enigma ciphers until his death in 1943. He built the team and discovered the method that broke the Italian Naval Enigma, producing the intelligence credited with Allied victory at the Battle of Cape Matapan. In 1941 Knox broke the Abwehr Enigma. By the end of the war, Intelligence Service Knox had disseminated 140,800 Abwehr decrypts, including intelligence important for D-Day.