The Bletchley Park Codebreakers

by Michael Smith

  The decrypts indicated that the situation on the ground was becoming ever more complex. As the Partisans moved to escape the Germans, the decrypts disclosed that they were confronted by Chetniks who were also intent on their annihilation. The Abwehr reported that the Chetniks in Herzegovina and Montenegro were preparing for large-scale operations against the Partisans at the end of March, with all men between the ages of thirteen and sixty being mobilized in the area for this purpose. The decrypts also revealed that there was a close relationship between the Italians and some Chetniks. This was already known to the British as a result of reports from Hudson, bur the decrypts showed that the Italians were seeking the consent of the Germans for the use of Italian-officered Chetnik units against the Partisans. Löhr would not agree, but, as he could not stop the Italian plans, he requested that they make every effort to ensure the Chetniks would not come into contact with Germans advancing from the west, in case Italian officers came under German fire. Decrypts showed that the Italians were supplying the Chetniks with weapons and transporting them in lorries to get into position against the Partisans. In fact, during March the Germans did not advance against the Partisans or attempt any action against the Chetniks. Many years later, it became clear that there had been a ceasefire between the Germans and the Partisans, initially for the exchange of prisoners, but also because the Partisans were negotiating with the Germans for recognition as combatants, and for possible joint action against the Chetniks. Hitler put an end to the negotiations. Two Abwehr decrypts had, however, revealed that one of their agents, a German who reported as Dr Baux, was in negotiation with the Partisans, although it was not clear what the negotiations were about.

  On 10 March, Talbot Rice prepared an appraisal on Weiss. General Davidson consequently advised the Chiefs of Staff and revealed the first signs of doubt about British policy with military intelligence stating that ‘it was impossible to advise whether we should stick to our current policy of supporting Mihailović but not the Partisans’. The SOE, military intelligence and the Foreign Office had not been greatly assisted by the reports from Bailey, who had only been able to suggest that the Partisans and the Chetniks should be allocated spheres of activity. Bailey himself accepted this was a forlorn hope. The Chiefs of Staff were provided not only with Talbot Rice’s report, but the complete file on Weiss. As a result, they decided on 20 March that the Partisans should be contacted, despite opposition from the SOE in London, although to the delight of the SOE in Cairo. During this time, Churchill continued to receive decrypts relating to the major events that were taking place in Yugoslavia and also received a summary of the decrypts from ‘C’ in March, but the Prime Minister was yet to play a decisive part in the development of British policy.

  During the German–Partisan ceasefire, Ultra enabled British intelligence to follow the course of a battle that ensued between the Chetniks and Partisans. In mid-March, a running battle took place along the Neretva river, which the Chetniks were unsuccessfully trying to prevent the Partisans from crossing. A decisive encounter took place around the Montenegrin town of Kalinovik between 20 and 25 March. Bailey had told the SOE that Mihailović had left his headquarters on 16 March without telling Bailey where he was going or for what purpose. Decrypts reported that Mihailović was directing the fight against the Partisans led by Tito around Kalinovik and that the Italians were transporting Chetnik reinforcements to the area. Numerous decrypted signals demonstrated that the fighting was severe. The town fell to the Partisans on 25 March, the battle against the Chetniks having been won. Dr Baux, who was on a mission in the area, reported that Mihailović barely escaped being taken prisoner by the Partisans. Many Montenegrin Chetniks were said to have joined the Partisans, whose numbers in the area were estimated at 30,000. By early April, some of the Partisans were reported by the Abwehr to have reached the area in Montenegro around Mount Durmitor, having engaged Italian forces and put them to flight. They were said to have captured large quantities of food, arms, including heavy mortars, and ammunition. On 21 April, the first message from ‘Walter’ (Tito) to the head of the Comintern was intercepted by the British, although it was not decrypted until many months later. Tito claimed that a large number of regions were under Partisan control and that they were now organizing in the towns and villages in Herzegovina and Montenegro. The Abwehr reported that Tito, whose existence was mentioned in their messages, had established his headquarters near Foca.

  A report, based on decrypts, was prepared for General Davidson and the Chiefs of Staff by MI3b on 23 April. It advised that Mihailović had gravely prejudiced his long-term position by mobilizing his men for the campaign against the Partisans, and had lost command of Herzegovina and probably Montenegro. It concluded that, despite 200 miles of running battle with German forces, the Partisans had retained sufficient vigour and organization to defeat the Chetniks decisively, that the Germans were still trying to complete the destruction of the Partisans, and that Mihailović and his Chetniks were in danger of becoming further identified with the Axis.

  Decrypts also revealed the details of Operation Schwarz against the Chetniks. On 2 May, a message sent by General Alfred Jodl, Head of Operations at OKW, to Löhr on Hitler’s instructions was intercepted. The operation was to be kept secret from the Italians, as they were not trusted to keep its existence from the Chetniks. An incident would be engineered to justify the Germans moving into Italian-occupied Herzegovina and Montenegro; the Chetniks would be rounded up and placed in prison camps rather than annihilated, as had been the plan with the Partisans in Weiss. Abwehr decrypts disclosed that fighting was still going on between Partisans and Chetniks and that one of Mihailović’s principal commanders, Pavle Djurisić, had fallen out with Mihailović as he wished to assist the Germans against the Partisans, a course of action Mihailović refused to contemplate. The Italians were still supplying the Chetniks and providing transport. On 13 May, the fabricated report that Chetniks had attacked German forces was decrypted as were subsequent German negotiations with the Italians who tried to protect as many of the Chetniks as they could when it became clear that the Germans were moving into their territory. The Germans advanced into Montenegro, taking Chetniks prisoner and disarming them. Decrypts showed that the German forces were also trying to surround and destroy the Partisans (including Tito) now concentrated around Mount Durmitor. As the Germans closed in, Deakin and an MI6 officer, a Captain Hunter, parachuted in to join Tito. Decrypts revealed that for the first time the Partisans were effectively surrounded and were at real risk of being wiped out. Abwehr and German army decrypts referred to the bitter fighting and repeated bombing of the Partisans. The battle was over by 14 June but it soon became clear, from the decrypts, that once again a substantial body of Partisans had escaped and that Tito had given orders that they should disperse and reform near Jajce in Bosnia. A decrypted report from Löhr on 22 June reported to the German High Command that 583 German soldiers and 7,489 Partisans had been killed, with the probability that the Partisans had lost another 4,000 men. Chetnik losses were put at 17, with nearly 4,000 taken prisoner. The contrast between the two resistance movements was stark.

  Churchill had been kept informed from his own reading of the decrypts and no doubt from briefings. By this time the Allies had decided, at the Trident Conference in Washington in May 1943, that the second front would be launched across the Channel in 1944, but that Sicily could be invaded during that summer with further operations in the Mediterranean if subsequently agreed. Churchill argued in a note circulated at the end of the Conference for the occupation of southern Italy, which would enable munitions and commandos to be sent across the Adriatic to Yugoslavia. On 12 June, after reading his decrypts, he asked for a report from the intelligence services on Yugoslavia. At the time a debate was still raging as to whether the British should provide assistance to the Partisans now that they had been contacted. Probably due to incompetence, the report was prepared by the Foreign Office and the SOE in London, neither of whom had access to Sigin
t. It recommended the continuation of wholehearted support for Mihailović, with contact with the Partisans being limited to trying to reconcile the two groups. The Chiefs of Staff wrote to the Foreign Office that they felt the report had given ‘insufficient weight to the value of the Partisans as a fighting force against the Axis’. They stated that it was clear from ‘information available to the War Office from Most Secret Sources that the Chetniks were hopelessly compromised with their relations with the Axis in Herzegovina and Montenegro and that … as the most formidable anti-Axis element outside Serbia the Partisans deserve the strongest support’. In their reply the Foreign Office grudgingly climbed down, agreeing to supplies being sent to the Partisans if the Chiefs of Staff were ‘satisfied from information at their disposal’ that the Partisans were sufficiently well organized and they would not hamper British efforts to unify the resistance.

  Churchill had had enough: he summoned a meeting on 22 June to discuss Yugoslavia, stating: ‘All this is of the highest importance.’ He had also received that day the decrypt of the report by Löhr on Partisan and Chetnik losses. The meeting concluded that military assistance could be sent to the Partisans and support maintained for Mihailović subject to conditions that he must actively offer resistance and refrain from collaboration with the Italians. Churchill now had the bit between his teeth. Three days before the invasion of Sicily, on 7 July, he sent a message to the British commander, General Alexander, saying that he presumed he had read the ‘Boniface’ about the heavy fighting in Yugoslavia. He also urged the seizing of the mouth of the Adriatic so that ships could be run into Dalmatian and Greek ports, although he recognized that ‘this was hunting in the next field’. On 11 July, the Prime Minister, no doubt having chewed the cud further, instructed that a 2,000–3,000-word digest be made of the Sigint reports about Yugoslavia, Albania and Greece, ‘showing the great disorder going on in these regions’. The digest is unfortunately not available, but after its receipt Churchill felt so impressed by its contents that he cabled Alexander to say that ‘it gave a full account of the marvellous resistance by the followers of Tito and the powerful cold-blooded manoeuvres of Mihailović in Serbia’.

  Having set out for Alexander the numbers of Axis divisions deployed, he wrote that, in his opinion, ‘great progress lay in the Balkan direction’. Churchill was sufficiently enthused with the report to direct that a copy should be delivered by hand to Alexander. Churchill agreed to upgraded missions being sent to both Tito’s and Mihailović’s headquarters. He personally briefed Fitzroy Maclean, who was being sent to the Partisans, dubbing him an ‘ambassador leader’. But the Prime Minister clearly cared not one jot who was to be sent to the Chetniks. While he had not finally made up his mind whether to withdraw support from the Chetniks, it was clear that he was set on a course to provide the Partisans with the maximum support possible, whatever the political consequences for postwar Yugoslavia.

  In the meantime, a message from Dimitrov to Tito in early July advised the Partisan leader to conserve his forces for future decisive fighting – a clear indication of the level of control exercised over him by Moscow. Abwehr decrypts indicated that Partisan groups were indeed making their way westwards from Mount Durmitor. During July, message after message was decrypted which indicated that the Germans feared an Allied invasion of the Balkans. The Abwehr advised Löhr that the Balkans would be ‘the main object of an Allied attack’. The German Foreign Ministry advised its Consul in Istanbul that ‘the Balkans would be the first to be invaded’. The head of the Italian Secret Service, General Cesare Amè, advised his German opposite number (he was not named in the decrypt but this was presumably Admiral Wilhelm Canaris, head of the Abwehr) that if Italy capitulated the Allies would turn their attention on the Balkans – his fears may have come about as a result of British disinformation. The possibility that the Germans feared Italian collapse was confirmed in a decrypted message from Ambassador Oshima to his government in Tokyo on 26 July, when he advised that Hitler had told him ‘he recognised the possibility of Italian collapse and was preparing for the worst; and that Germany must strengthen her defences in the Balkans’. The Allies invaded southern Italy on 3 September. The final decision not to invade the Balkans had been taken at an Allied Conference in Quebec in August, which also decided that the Allies’ involvement in that part of the world would be limited to supplying arms to the guerrillas, bombing strategic objectives, and minor commando raids.

  Prior to this, the decrypts revealed that the Italians were effecting a withdrawal and that the Germans were positioning their limited forces to try to prevent a vacuum which could be exploited by the resistance or the Allies. On 7 August, the German Consul in Dubrovnik reported that the Italians were withdrawing from the hinterland and were moving Chetniks into position to cover their retreat. The German liaison officer with the Italian 2nd Army advised that his impression was that they were making ‘a planned evacuation little by little’. Abwehr reports indicated that the Italians were offering arms to Chetniks to cover their withdrawal. Messages from the German naval commander were decrypted, which revealed his plans to seize Italian naval installations and ports. The German plans for reorganizing their army commands in north Italy and the Balkans were read. Decrypts disclosed movement of German forces into the Italian zone, and the occupation of Italian airfields. Some Chetniks, seeing the way the wind was blowing, sought to collaborate with the Germans. Intercepted reports from Dr Baux detailed the negotiations that he was having with the Chetnik leader in Herzegovina, Jevdjević, who was offering to deploy 5,000–6,000 Chetniks in co-operation with the Germans against the Partisans. A Sicherheitsdienst report confirmed what the British also thought from their intelligence, that Mihailović would only act if and when the Allies invaded the Balkans.

  On 9 September, Italy capitulated. A decrypt of a message from the German Foreign Ministry announced that Hitler had foreseen Italy’s collapse, that all measures had been taken and that German troops were marching. German Army Commander South East claimed on 12 September that ‘the south east is firmly in our hands’. The decrypts revealed that the reality was different. The SS Prinz Eugen Division, recruited from local ethnic Germans, reported encountering stiff resistance from Italian forces who refused to surrender, although in Dubrovnik, the consul Aelbert signalled that after negotiations 28,000 Italians had decided not to fight. An earlier decrypt of a message sent by Aelbert to the commanding officer of the Prinz Eugen Division shed light on some of its activities. Aelbert complained that those reported to him included the shooting of ‘25 children as young as eight months’, which he described as ‘counterproductive’ and ‘having an extremely bad effect on the population’. The Prinz Eugen Division then fought a sixteen-day battle with Italian troops as it tried to move along the coast to take Split. In Montenegro, decrypts revealed that the Germans fought battles with the Italians until November. Decrypts also disclosed the actions of the resistance. The Partisans seized Split from the Italians, capturing large quantities of arms and supplies, and were joined by many Italians. On the German approach to the town, the Partisans moved away, the Abwehr reporting that Tito then intended to carry out ‘major operations’ in north Croatia and Slovenia. An Abwehr officer voiced the opinion, in a report on 21 September, that the ‘total situation’ in Croatia had got worse as a result of the actions of the Partisans. But decrypts also revealed that the Germans had largely dealt with the Italian problem by mid-October, when a report revealed that over 10,000 Italian officers and a quarter of a million men were being removed from Yugoslavia. There were no reports of Chetnik activity. The British knew from their liaison officers that Mihailović had told his men not to carry out sabotage or engage the Germans. Decrypts also disclosed that the Germans were moving their killing squads, the Einsatzgruppen, into the former Italian zone to seize Jews and others.

  Decrypts between Tito and Dimitrov subsequently revealed the Partisan leader’s complaints that the British had not informed him of the date of Italian capitul
ation and that the British sent spies to the Partisans rather than supplies – a view that at that time was entirely correct, Maclean having arrived to join Deakin on 18 September. They also revealed that Dimitrov had told Tito the Russians would be sending him a mission. Tito’s immediate response was to send a shopping list, including a request for ‘several tens of suits for our generals and colonels’. Shortly afterwards, Dimitrov rebuked Tito for sending over-long reports.

  At the end of September, Talbot Rice prepared a detailed assessment. He confirmed that there had been only isolated anti-German activity by Mihailović, but that ‘the heroes of the hour are undoubtedly the Partisans’, who had seized large stretches of the coast. He advised that the Partisans were successfully embarrassing the Germans and that their ‘military efforts deserve all the support we can give them’. He further recommended Mihailović should be told to destroy German lines of communication in Serbia and be warned that if he failed to do so, Tito would be the sole recipient of British aid which they were at long last in a position to deliver. In the space of six months, the evidence from Sigint had completely changed the view of Talbot Rice, and MI3b.