Editing Battle of Crete (section)

===Ultra===
[[File:Enigma 04.jpg|thumb|[[Enigma encryption machine]], 1940]]
For a fortnight, Enigma intercepts described the arrival of ''Fliegerkorps XI'' around Athens, the collection of 27,000 [[Register ton|registered tons]] of shipping and the effect of air attacks on Crete, which began on 14 May 1941. A postponement of the invasion was revealed on 15 May, and on 19 May, the probable date was given as the next day. The German objectives in Crete were similar to the areas already being prepared by the British, but foreknowledge increased the confidence of the local commanders in their dispositions. On 14 May, London warned that the attack could come any time after 17 May, which information Freyberg passed on to the garrison. On 16 May the British authorities expected an attack by 25,000 to 30,000 airborne troops in {{nowrap|600 aircraft}} and by 10,000 troops transported by sea. (The real figures were 15,750 airborne troops in {{nowrap|520 aircraft}} and {{nowrap|7,000 by}} sea; late decrypts reduced uncertainty over the seaborne invasion.) The British mistakes were smaller than those of the Germans, who estimated the garrison to be only a third of the true figure. (The after-action report of ''Fliegerkorps XI'' contained a passage recounting that the operational area had been so well prepared that it gave the impression that the garrison had known the time of the invasion.{{sfn|Hinsley|1994|pp=82–84}})

The Germans captured a message from London marked "Personal for General Freyberg" which was translated into German and sent to Berlin. Dated 24 May and headed "According to most reliable source" it said where German troops were on the previous day (which could have been from reconnaissance) but also specified that the Germans were next going to "attack Suda Bay". This could have indicated that Enigma messages were compromised.<ref>{{cite book |last=Sebag-Montefiore |first=Hugh |title=Enigma: The Battle for the Code |orig-date=2000 |year=2017 |publisher=Weidenfeld & Nicolson |location=London |isbn=978-1-4746-0832-9 |page=181}}</ref>

[[Antony Beevor]] in 1991 and P. D. Antill in 2005 wrote that Allied commanders knew of the invasion through [[Ultra (cryptography)|Ultra]] intercepts. Freyberg, informed of the air component of the German battle plan, had started to prepare a defence near the airfields and along the north coast. He had been hampered by a lack of modern equipment, and the lightly armed paratroopers had about the same firepower as the defenders, if not more. Ultra intelligence was detailed but was taken out of context and misinterpreted.<ref>{{harvnb|Beevor|1991|loc= Appendix C}}.</ref><ref>{{cite book |last1=Handel |first1=Michael I. |year=1990 |editor1-last=Handel |editor1-first=Michael |title=Intelligence and Military Operations |url=https://books.google.com/books?id=zZLcAAAAQBAJ |series=Studies in Intelligence |location=Abingdon, Oxfordshire |publisher=Routledge |publication-date=2013 |page=47 |isbn=978-1-135-17934-2 |access-date=23 July 2018 |quote=It appears that General Freyberg was introduced to Ultra only shortly before the battle of Crete began and therefore had no time to become familiar with its proper interpretation. This situation was exacerbated by the fact that 'he was forbidden to show it (the information derived from Ultra) to anyone or to discuss it with his intelligence staff.' [...] Moreover, tight security regulations prohibiting him from taking action on the basis of uncorroborated Ultra evidence limited its value. |archive-date=28 September 2019 |archive-url=https://web.archive.org/web/20190928073132/https://books.google.com/books?id=zZLcAAAAQBAJ |url-status=live}}</ref>
While emphasis was placed on the airborne assault, the German messages also mentioned seaborne operations; Freyberg, expecting an amphibious landing, garrisoned the coast – which reduced the number of men available to defend the airfield at Maleme, the principal German objective.<ref>{{harvnb|Antill|2005|p=36}}.</ref> In 1993, [[F. H. Hinsley]], the official historian of British intelligence during the war, wrote that the Germans had more casualties in the conquest of Crete than in the rest of the Greek campaign; the 7th ''Fliegerdivision'' was decimated, leaving the Germans with a crippled airborne arm. <!-- I can only find the 1979 original edition, on archive.org https://archive.org/details/britishintellige00hins_0/page/420/mode/1up, p. 420 which seems to have much the same content. Can't be arsed to rebuild the cite and all the sfns, sorry--> It was the only unit of its kind and was not rebuilt.{{sfn|Hinsley|1994|p= 84}}

Hinsley wrote that it was difficult to measure the influence of intelligence gained during the battle, because although Ultra revealed German situation reports, reinforcement details and unit identifications, and although more intelligence was gleaned from prisoners and captured documents, it was not known how swiftly the information reached Freyberg or how he used it. The German parachute warfare manual had been captured in 1940, and after the war Student said that he would have changed tactics had he known this. Field-signals intelligence was obtained, including bombing instructions and information from the ''Fliegerkorps'' XI tactical code. Lack of air cover prevented much British air reconnaissance north of Crete, but on 21 May signals intelligence enabled an aircraft to spot a convoy. After midnight the navy sank twelve ships and the rest scattered, which led to a second invasion convoy being called back. The second convoy was intercepted during the morning of 22 May, despite the cost to the navy of a daylight operation, and no more seaborne attempts were made.{{sfn|Hinsley|1994|pp=84–85}}