'Halyard' was a US airborne operation by the Office of Strategic Services to rescue US aircrew from German-occupied Yugoslavia (2 August/27 December 1944).

The US team was commanded by Lieutenant George Musulin, along with Master Sergeant Michael Rajacich, and Specialist Arthur Jibilian as the radio operator. Allocated to Major General Nathan F. Twining’s Italy-based US 15^th AAF, the team was designated as the 1^st Air Crew Rescue Unit.

Following the Allies' successful 'Husky' (i) invasion and the subsequent capture of Sicily, Italy capitulated to the Allies on 8/9 September 1943 and the Allies were able to occupy the whole of southern Italy including, in the south-east, the area round Foggia. It was to an airfield in this area, on 1 December 1943, that the 15^th AAF was transferred from Tunisia. This airfield became the largest US air base in southern Italy, and from it and associated airfields (Bari, Brindisi, Lecce and Manduria) were launched attacks on targets in southern and eastern Europe, and most especially in Germany, Hungary, Slovakia, the notionally independent state of Croatia, occupied Serbia, Bulgaria and Romania. Some of the most important targets were the oilfields and refineries in Romania, for these were among the most important driving forces of the German war machine. The Ostro Romano refinery in Ploieşti, to the north of Bucharest, provided more than one quarter of all Germany’s fuel needs and was one of the priority targets. All flights targeting the oilfields and refineries in Romania passed over the Gebiet des Militärbefehlshabers in Serbien (Territory of the Military Commander in Serbia).

Between October 1943 and October 1944, the 15^th AAF flew about 20,000 bomber and fighter sorties, and in the same period lost almost 50% of its aircraft but only some 10% of its personnel. To carry out its combat missions, the 15^th AAF possessed about 500 Boeing B-17 Flying Fortress and Consolidated B-24 Liberator heavy bombers, and about 100 escort fighters.

The flight path from southern Italy across the Adriatic Sea, Montenegro, Serbia and Bulgaria to targets in Romania was used every day from the spring of 1944, and some 65% of these flights were directed against objectives in Bulgaria, Romania and the German-occupied zone of Serbia. In these regions the Germans had only a limited number of fighters, and these generally targeted bombers damaged by the Axis anti-aircraft defences in Bulgaria and Romania.

In the spring of 1944, the USAAF intensified the bombing of targets in Bulgaria and Romania, and as a result larger numbers of US aircrew had to bail out of damaged aircraft over occupied Yugoslavia. Some of these men fell into the hands of Romanian, Bulgarian, Croat or German troops and were sent to prisoner of war camps. By August 1944, 350 bombers had been lost, and many of their crew members escaped immediate relegation to prisoner of war camps as they came down in territory held by Marshal Josip Broz Tito’s partisan forces or found refuge in Serbia with the Četnik forces of Diviziski General Dragoljub 'Draza' Mihailović.

The first US airmen bailed out over the German zone of Serbia on 24 January 1944, the day on which two Liberator bombers were shot down, one over Zlatibor and the other over Toplica. Another bomber, damaged by German fighters, crash-landed between Pločnik and Beloljin, and its nine-man crew was rescued by the Četnik 'Toplica' Corps under the command of Major Milan Stojanović, who organised for the US men to be placed in the home of local Četnik leaders in the village of Velika Dragusa. Another bomber was shot down on the same day, the crew bailing out over Mt Zlatibor and being found by members of the 'Zlatibor' Corps. Stojanović informed Mihailović of the rescue of one of the crews on 25 January.

By a time early in July 1944, more than 100 airmen were in areas under Četnik control. The German and Bulgarian occupation forces in Serbia had spotted escape of many of the US airmen by parachute, but many of them were spirited away by the Četniks before the occupation forces could reach them. The Germans offered cash rewards to the Serb population for the capture of Allied airmen, but local peasants accepted the airmen into their homes and fed them for months, and medical facilities for sick and wounded airmen were established in Pranjani.

The Office of Strategic Services had already secured Tito’s co-operation for the retrieval of downed airmen. In January 1944 Major Linn M. Farish and Lieutenant Eli Popovich had parachuted into Yugoslavia to reach the partisan headquarters at Drvar and start arranging aid in the rescue of US airmen. Following a meeting between the OSS team and Tito on January 23, orders went sent to all partisan units to do everything possible to locate downed airmen and conduct them safely to the nearest Allied liaison team.

Efforts to retrieve airmen from Četnik-controlled areas were hampered by the complexities of Balkan politics. The British considered that part of the world to lie within their sphere of interest, and had shifted their support from Mihailovic to Tito, and were determined to sever all ties with Mihailović lest they offend Tito, and US attempts to maintain contact with Mihailović had caused concern in London. Twining was nonetheless determined to rescue his downed airmen. On 24 July, as a result of the efforts of Twining and several OSS officers, Lieutenant General Ira C. Eaker, the commander of the Mediterranean Allied Air Forces, directed the 15^th AAF to create an aircrew rescue unit (ACRU). This was to be attached to the 15^th AAF and assume responsibility for the location and recovery of Allied airmen throughout the Balkans.

The head of the ACRU was Colonel George Kraigher of the AAF Transport Command. This officer had flown with the Serb air arm in World War I, and before World War II had played a key role in developing Pan American Airways' air route from Miami to the Middle East via Brazil and West Africa. On assuming command of the ACRU, Kraigher formed two parties, one to work with Tito’s partisans and the other with Mihailović's Četniks.

Musulin, an OSS officer who had led a liaison mission to Mihailović and one of the foremost advocates of maintaining contact with the Četniks, was named commander of ACRU 1, otherwise known as the 'Halyard' Mission. Master Sergeant Michael Rajacich, borrowed from the OSS Secret Intelligence Branch, and Specialist 1^st Class Arthur Jibilian, the mission’s navy OSS radio operator, completed ACRU 1.

On the night of 2/3 August 1944, after several abortive attempts, the 'Halyard' team was parachuted into the area of Mihailović's headquarters at Pranjani. Musulin then arranged a meeting with a committee of the airmen to discuss the preparations needed for an evacuation, and learned that there were about 250 airmen divided into six groups and accommodated within a 10-mile (16-km) radius of the airstrip at Galovića Polje near Pranjani. Musulin established a daily courier service between the mission and the various groups to advise on the progress of the undertaking, and also distributed funds to enable the airmen to purchase supplies. At the same time Mihailović assigned the 1^st 'Ravna Gora' Corps to provide security.

According to statistics compiled by the US Air Force Air Crew Rescue Unit, in the period between 1 January and 15 October 1944 a total of 1,152 US aircrew were airlifted from Yugoslavia, 795 with the assistance of the Yugoslav partisans and 356 with the aid of the Serb Četniks

Early in March 1944, 25 rescued pilots were brought to Pranjani with Captain Zvonimir Vučković of the 1^st 'Ravna Gora' Corps responsible for their security. Mihailović ordered Vučković to improvise an improvised airstrip from which the airmen could be evacuated, and Vučković selected a field near Pranjani. Construction was managed by Captain Nikola Verkić, and most of the work was undertaken at night by a force of more than 100 persons and as many ox-drawn carts.

The British believed that the airstrip was too short and 11 airmen wanted to go on foot to the Adriatic Sea for seaborne evacuation. Mihailović provided supporting units, and the 11 men set off on 19 April. The remaining aviators were unable to walk as a result of injuries and illness, and a few dozen more airmen reached Pranjani in late April. Vučković divided those at Pranjani into two groups: the first of these, from the Takovo district, was guided by Sergeant Bora Komračević, and the second, from the Dragačevo district, by Mihailo Paunović, who spoke no English.

The occupation forces knew that downed airmen were being collected in the Pranjani area, and this led to combat between the Četniks and the German and Bulgarian occupation forces. On 14 March the Germans moved into the village of Oplanić, near Gruzа, looking for the crew of a downed Liberator. Captain Nikola Petković's 4/'Gruza' Brigade opened fire on the German light armoured vehicles in an effort to lure them away from the portion of the village where the airmen were hiding, and three Četniks were killed and two captured during the firefight.

There were several other engagements.

The British Special Operations Executive’s military mission to the Četniks, led by Brigadier C. D. Armstrong, was ready for evacuation by a time late in May 1944, and three Douglas Dakota cargo aircraft landed at Pranjani on 29 May to collect the British team, 40 rescued airmen and the members of the political mission Mihailović had decided to send to London in an effort to persuade British political leaders to urge Prime Minister Winston Churchill not to abandon Mihailović and switch British support to Tito. The mission was a failure as the mission was not allowed to leave southern Italy.

As of a time late in May 1944, for the first time since 1941 there were no Allied liaison officers with the Četniks. Mihailović's headquarters had attempted but failed to establish direct radio contact with the Allied command in the Mediterranean theatre. Late in July 1944, one of the rescued airmen, a radio specialist, was able to establish a connection with his own base in Italy. This officer was a Major Brooks, whose aeroplane had made an emergency landing near Ljig. A detachment of the 'Rudnik' Corps, led by Captain Dragomir Topalaović, engaged the Germans to keep them away from the aeroplane while the Americans and Četniks stripped it of equipment including the radio equipment. Brooks was thus able to establish contact with the Allies, and was able to confirm the accuracy of the information supplied by Vujnovich.

During the night of 2 August 1944, a US aeroplane flew over Pranjani, near Mihailović's headquarters in central Serbia, where a fire burned as the agreed signal, and Musulin, Rayachich and Jiblian jumped with their radio equipment to set up the rescue operation. Musulin’s first task was to request Mihailović to gather all the rescued airmen in the area for the forthcoming evacuation, and in case of a German attack on Pranjani, Mihailović was asked to build a back-up airstrip in the Dragačevo area. Mihailović decided to use this opportunity to send a four-man political team to Italy to assist Topalović with his mission.

The largest evacuation from Pranjani began at 03.00 on 10 August, when 10 (or according to other sources 12 or 14) C-47 aircraft arrived, possibly escorted by as many as 50 fighters of the 15^th AAF or, according to another source, six British Supermarine Spitfire fighters. Some 237 men were evacuated in the C-47 aircraft.

The undertaking was repeated on 12, 15 and 18 August, when another 210 airmen were evacuated.

A new OSS unit, under the command of Colonel Robert H. McDowell, was now to continue the undertaking as 'Ranger'. Musulin left of Pranjani on 29 August in the aeroplane which delivered McDowell, and Musulin’s replacement, Captain Nick Lalich, had reached Pranjani by air on 10 August.

On the eve of the arrival of Soviet forces in Yugoslavia during September 1944, the command of what was now the Yugoslav army, along with the 'Halyard' and 'Ranger' missions, transferred from Pranjani to Mačva. Another airstrip had been improvised at Koceljeva between 15 and 17 September with a 1,315-ft (400-m) runway, and from this one Frenchman, a few Italians and two US medical officers were evacuated on 17 September.

A third improvised airstrip was built between 22 October and 1 November at Boljanić, near Doboj in eastern Bosnia, and this was used to evacuate the supreme command of the Yugoslav army and 15 US airmen on 27 September after two C-47 aircraft, covered by seven fighters, had landed. The evacuees, including Captain John Milodragovich and Lieutenant Michael Rajachich of the OSS, were flown to Bari.

On 27 December two C-47 aircraft, one flown by Kraigher and the other by 1^st Lieutenant John L. Dunn, left Italy at 11.00 and, escorted by 16 Lockheed P-38 Lightning fighters, arrived over the airstrip at Boljanić at 12.55. Spotting a hole in the overcast, Kraigher led the way to land on a 1,700-ft (520-m) strip frozen just hard enough to support the weight of a C-47. The transport aircraft were met by Lalich, and quickly loaded with 20 US airmen, one US citizen, two Četnik officers, four French and four Italian army personnel, and two remaining members of the 'Halyard' team, Lalich Jibilian. The aircraft took off at 13.15 and returned to Italy.

The numbers of airmen who were rescued was thus 237 from Pranjani on 9 and 10 August, 210 from Pranjani on 12, 15 and 18 August, 20 from Koceljeva on 17 September, 15 from Boljanić on 1 November, and 20 from Boljanić on 27 December for a total of 417 Allied airman including 343 Americans.