What do the British Official Historians Say about Codebreaking Evidence of Gas Chambers in Nazi Camps?

Between 17 and 25 May 1943, following the breaching of the Möhne dam, a special but readable cypher was used in the Ruhr. It carried orders to police and other organisations in the affected areas; the decrypts showed that the emergency was quickly controlled

From the spring of 1942 until February 1943, when it ceased to be sent by WIT, GC and CS decrypted in another cypher a daily return of prisoners at Dachau, Buchenwald, Auschwitz and seven other concentration camps – not all of them, but a good cross section.* The daily return consisted of a series of unheaded, unexplained columns of figures which GC and CS worked out to mean (a) number of inmates at the start of the previous day, (b) new arrivals, (c) departures by any means, and (d) number at the end of the previous day. It also specified the various categories of prisoner, such as politicals, Jews, Poles, other Europeans and Russians. GC and CS interpreted column (c) – ‘departures by any means’ – as being accounted for primarily by deaths. The returns from Auschwitz, the largest of the camps with 20,000 prisoners, mentioned illness as the main cause of death but included references to shootings and hangings. There were no references in the decrypts to gassing. There were to be other references to concentration camps in the police traffic of later years, but they were infrequent.**