Editing Signals intelligence (section)

===Postwar consolidation===
With the importance of interception and decryption firmly established by the wartime experience, countries established permanent agencies dedicated to this task in the interwar period. In 1919, the British Cabinet's Secret Service Committee, chaired by [[Lord Curzon]], recommended that a peace-time codebreaking agency should be created.<ref name="johnson">{{cite book |first=John |last=Johnson |title=The Evolution of British Sigint: 1653–1939 |year=1997 |publisher=HMSO |asin=B002ALSXTC|page=44}}</ref> The [[Government Code and Cypher School]] (GC&CS) was the first peace-time codebreaking agency, with a public function "to advise as to the security of codes and cyphers used by all Government departments and to assist in their provision", but also with a secret directive to "study the methods of cypher communications used by foreign powers".<ref>{{cite book |first=Michael |last=Smith |chapter=GC&CS and the First Cold War |title=Action This Day: Bletchley Park from the Breaking of the Enigma Code to the Birth of the Modern Computer |editor1-first=Michael |editor1-last=Smith |editor2-first=Ralph| editor2-last=Erskine |publisher=Bantam Press |year=2001 |isbn=978-0-593-04910-5|pages=16–17}}</ref> GC&CS officially formed on 1 November 1919, and produced its first decrypt on 19 October.<ref name="johnson" /><ref>{{cite book|first=Paul|last=Gannon|title=Inside Room 40: The Codebreakers of World War I|publisher=Ian Allan Publishing |year=2011 |isbn=978-0-7110-3408-2}}</ref> By 1940, GC&CS was working on the diplomatic codes and ciphers of 26 countries, tackling over 150 diplomatic cryptosystems.<ref>David Alvarez, GC&CS and American Diplomatic Cryptanalysis</ref>

The [[Black Chamber|US Cipher Bureau]] was established in 1919 and achieved some success at the [[Washington Naval Conference]] in 1921, through cryptanalysis by [[Herbert Yardley]]. Secretary of War [[Henry L. Stimson]] closed the US Cipher Bureau in 1929 with the words "Gentlemen do not read each other's mail."