Editing Cryptanalysis of the Enigma (section)

===Major setback===
On 15 December 1938, the German Army increased the complexity of Enigma enciphering by introducing two additional rotors (IV and V). This increased the number of possible ''wheel orders'' from 6 to 60.<ref name=Kozaczuk84p54>{{Harvnb|Kozaczuk|1984|p=54}}</ref> The Poles could then read only the small minority of messages that used neither of the two new rotors. They did not have the resources to commission 54 more bombs or produce 58 sets<!-- They had 2; they needed 58 other sets. --> of Zygalski sheets. Other Enigma users received the two new rotors at the same time. However, until 1 July 1939 the ''[[Sicherheitsdienst]]'' (SD)—the intelligence agency of the [[Schutzstaffel|SS]] and the [[Nazi Party]]—continued to use its machines in the old way with the same indicator setting for all messages. This allowed Rejewski to reuse his previous method, and by about the turn of the year he had worked out the wirings of the two new rotors.<ref name=Kozaczuk84p54/> On 1 January 1939, the Germans increased the number of plugboard connections from between five and eight to between seven and ten, which made other methods of decryption even more difficult.<ref name=RejewskiAppxC242/>

Rejewski wrote, in a 1979 critique of appendix 1, volume 1 (1979), of the official history of British Intelligence in the Second World War: {{blockquote|we quickly found the [wirings] within the [new rotors], but [their] introduction ... raised the number of possible sequences of [rotors] from 6 to 60 ... and hence also raised tenfold the work of finding the keys. Thus the change was not qualitative but quantitative. We would have had to markedly increase the personnel to operate the bombs, to produce the perforated sheets ... and to manipulate the sheets.<ref name=RejewskiHinsleyP80>{{Harvnb|Rejewski|1982|p=80}}</ref><ref>Also quoted in {{Harvnb|Kozaczuk|1984|p=63}}</ref>}}