'Astrolabe' was a British Jeep-mounted special forces raid from the mouth of the Tenna river in Italy by 'Popski’s Private Army' (14/15 June 1944).

Popski’s Private Army was one of the several semi-regular special forces units spawned by the British during the Western Desert campaign, and its leader was Lieutenant Colonel Vladimir Peniakoff, a Belgian-born Jewish officer with unconventional ideas about discipline and tactics. The unit was formed as No. 1 Demolition Squadron, PPA, during 1942. Specialising in raids (but not quite in the same form as the Special Air Service and Long Range Desert Group), the PPA caused problems to the Axis force throughout the North African and Italian campaigns. The PPA also caused problems for some of the more conservative elements of the Allied forces, and more than one staid senior officer got into trouble for encountering a member of the unit in the street and putting the man on a charge because he answered 'Popski’s Private Army' when asked the name of his unit.

Although it came into existence too late to be involved in 'Lightfoot' and 'Supercharge' (the first and second phases of the 2^nd Battle of El Alamein), the PPA did find an operational role in the period between November 1942 and the end of the North African campaigns in May 1943, although events proceeded so rapidly as the Axis force were driven into their final lodgement in northern Tunisia that the PPA’s opportunities were limited. in March 1943 a joint patrol of the PPA and Long Range Desert Group discovered the so-called Wilder’s Gap in the Matmata hills that made it possible for the armour of General Sir Bernard Montgomery’s British 8^th Army to outflank the positions of Generalfeldmarschall Erwin Rommel’s Deutsch-Italienische Panzerarmee along the Mareth Line in 'Pugilist Gallop', and the PPA was among the first elements of the 8^th Army, pushing to the west, to meet the forward elements of Lieutenant General K. A. N. Anderson’s Allied 1^st Army and Lieutenant General Lloyd R. Fredendall’s US II Corps as they pushed to the east in Tunisia early in 1943. Many PPA raiding and reconnaissance operations were carried out around the time of the 'Battle of the Kasserine Pass', resulting from the German 'Frühlingswind' and 'Morgenluft', and included taking the surrender of 600 Italians.

The PPA spent the summer of 1943 in Algeria and Tunisia recruiting and training volunteers from the LRDG, SAS, Commandos and Royal Armoured Corps in preparation for the movement of the war to Italy, bringing the unit’s size up to about 35 all ranks, with two fighting patrols and a small headquarters. For a short while the PPA trialled the use of the gliders of Major General F. A. M. Browning’s British 1^st Airborne Division to deliver it and its Jeeps for operations behind the Axis lines in Sicily, but the unit’s part in 'Husky (i)' was cancelled at the last minute.

In September 1943 an advance patrol of the PPA was delivered by sea to Taranto after 'Slapstick' and headed inland, and here the PPA secured a major intelligence victory by discovering the weakness of Generalmajor Richard Heydrich’s 1^st Fallschirmjägerdivision opposing the 1^st Airborne Division. As a result of this success Peniakoff was allowed to increase the size of PPA to 80 all ranks, but throughout the Italian campaign usually had about 100 men at any one time. The PPA was unusual in that all recruits, including officers, on joining the unit reverted to the lowest rank of private or 2^nd lieutenant. The unit was run quite informally: there was no saluting and no drill, officers and men messed together, every man was expected to know what to do and get on with it, and there was only punishment for failure of any kind was an immediate return to unit. One tactical headquarters patrol in four Jeeps and three fighting patrols each of 18 men in six Jeeps were formed and given great autonomy. Each Jeep was armed with 0.5- and 0.3-in (12.7- and 7.62-mm) machine guns, giving the patrols immense firepower for their size. The men received extensive and arduous training for amphibious, mountain and parachute operations, demolition and counter-demolition, reconnaissance and intelligence gathering.

During this long operational hiatus several operations were projected and cancelled, including a scheme for the PPA to take part in the 'Shingle' landing at Anzio.

The only operation undertaken the PPA in Italy was 'Astrolabe' in June 1944. Some 50 men of Patrols A, B and R, together with 12 Jeeps, were ferried to a location in the Marche region, about half way along the east coast of Italy, and landed behind the German lines between Pescara and Ancona to provide intelligence and undertake sabotage in connection with the 8^th Army’s summer offensive. Captain Robert Yunnie, two other British soldiers and two Italian partisan guides were to be landed first by launch as an advance force. This advance party would then meet the landing craft carrying the rest of the party, guide it in, and inform Peniakoff of the local situation. But as soon as the advance guard got ashore, Yunnie realised that the situation was all wrong. The British offensive had already succeeded, and the roads were jammed with retreating Germans. Even so, Yunnie decided to signal the landing craft to approach the shore, and leave to Peniakoff the decision of what should be done. Although the clogged roads meant that the PPA would have great risk and difficulty in reaching an area in which it could operate, there was great potential for hit-and-run attacks on the retreating Germans. But when Peniakoff learned of the situation he cancelled the undertaking. The PPA could have had a brief moment of glory blasting retreating vehicles, but these were loaded with experienced Germans troops and were interspersed with armoured cars and tanks. Even if initially successful, a PPA attack would inevitably had ended with defeat. Peniakoff therefore instructed Yunnie to go back ashore with his men, together with two more, to provide intelligence, and gave the order for 'Astrolabe' to be called off. However, the landing craft ran aground, could not be refloated, and had to be abandoned. All the men were transferred safely to the accompanying motor launch, but the Jeeps and all the supplies were lost.

Yunnie’s reinforced advance guard at first stayed at the farmhouse of friendly Italian peasants and then, for greater security, moved out into the country. They laid up by day and sortied at night, identifying targets for Allied air attacks. Yunnie’s detachment continued to watch the roads and call in air attacks until the British forces reached the Fermo river valley. Here the Germans retreated before the leading formation of Generał dywizji Władysław Anders’s Polish II Corps arrived, so for a brief moment Yunnie was the military governor of Fermo, where he tried to limit the excesses of partisan retribution. After the arrival of the Poles, Yunnie commandeered a car and travelled to join Peniakoff in Sarnano.

After calling off 'Astrolabe', Peniakoff had returned to his headquarters at San Gregorio near Brindisi, and led the balance of the PPA, in 10 Jeeps, to the north on the eastern side of the Apennine mountains into the area in which he knew that the British advance would give him scope for operations. Operating in the foothills of the Apennine mountains, the PPA had a considerable area in which to manoeuvre, was not hindered by the presence of 8^th Army troops, and could easily locate German elements preparing to hold their ground. Near Camerino, Peniakoff encountered an effective partisan unit led by Maggiore Antonio Ferri and his brother. The partisans had gained control of a valley in the mountains, and were well disciplined. Peniakoff suggested that the PPA and partisans join forces to create a force able to expel the Germans from the area. This was a considerable undertaking for a small force, for an unknown number of Germans held Camerino, which was a walled town on high ground. Neither the PPA nor the partisans had heavy weapons, and when they approached the town they were quickly driven back by mortar fire. Realising that the weakness of the German position was its line of supply and communication, Peniakoff ordered a bridge to be mined, but not effectively as he did not wish the Germans to look for alternate routes. After allowing him to see a doctored map showing a British advance enveloping Camerino, a prisoner was then allowed to escape. The PPA then used its Jeeps to advance on Camerino and then fall pack under mortar fire, the retreat being enlivened by the activation of a smoke generator on Peniakoff''s Jeep to cover the retreat. The German commander then opted to fall back during the night while being harassed by the PPA and partisans.

After this success the PPA headed north. Yunnie’s B patrol moved into the mountains to the village of Esanatoglia, where he established a headquarters in an abandoned monastery and recruited an Italian ex-officer nicknamed 'Gigi' who served with the PPA until the end of the war. Suddenly receiving a premonition. Yunnie roused his patrol he headed over the mountain, leaving behind one of his original partisan guides, who had become very ill but rejoined a few days later. On retaking the monastery and finding it empty, the Germans had shot up the town and its partisan band, but the guide escaped by pretending idiocy.

By October the 8^th Army had broken through the 'Gotisch-Linie' defences in 'Olive', and again the Allied leadership hoped that the Germans would break and flee, with Peniakoff anticipating that his PPA would thereby be offered the opportunity to exploit a pursuit in the widest sense of the word. However, the Germans did not break, and fell back to the north in good order, slowing the British pursuit by blowing bridges and resisting obstinately. Even so, the situation as the PPA advanced toward Ravenna was extremely fluid. German groups, both large and small, some of them determined to fight to the last and others ready to surrender, held towns and strongpoints. The British were advancing, but were not particularly strong, since the main Allied thrust up the Italian peninsula was that to the west of the Apennine mountains by Lieutenant General Mark W. Clark’s US 5^th Army, and troops from the Italian campaign had been diverted to bolster the 'Dragoon' (i) invasion of southern France. The situation was rendered complex by the fact that there were large numbers of Italian partisan groups active with their own agendas, and that groups of Allied prisoners of war, many of whom had been on the loose for over a year, were hiding or moving in many places. This was an ideal situation for the PPA which, for increased mobility, had acquired DUKW amphibious trucks large enough to hold an armed Jeep. These ungainly craft were very useful in operating in the water-logged landscape, and allowed approaches from the sea. Peniakoff himself was absent in hospital in Rome with probably the first indications of the brain tumour which killed him in 1951, and command of the PPA devolved onto a French officer, Lieutenant Jean Caneri, who had been responsible for the PPA’s administration and was eager to get out in the field.

Near Ravenna the PPA had another good experience with partisans, in the form of the 52^nd Garibaldi Brigade. The PPA supplied weapons, and the combination of the brigade’s local knowledge and tenacity, and the PPA’s mobility, firepower and military skills made life very difficult for the German units still in the area. As it had often been taken under German mortar fire and respected the weapon, B Patrol obtained a mortar, which it put to good use, and also acquired a bazooka anti-tank rocket launcher.

On 9 December 1944, while the PPA was working with the 27^th Lancers of 'Porter' Force, some of the lancers' armoured cars were surprised by the Germans and their crews took refuge in a farmhouse. The lancers reported that they would have to surrender if they were not relieved before the evening. A PPA patrol of five Jeeps moved up the only approach and, covered by the fire of a troop of tanks 600 yards (550 m) away, drove up to the Germans. These were two companies of infantry dug in on a canal bank. Despite heavy German shelling, the patrol came to within 30 yards (27.5 m) of the Germans and opened fire. In a 50-minute action, in which the PPA and lancers fired some 25,000 rounds, the lancers in the farm were evacuated and the Germans fled, leaving 80 dead. The only British casualties were Peniakoff, who had his right hand blown off, and two men of B Patrol who were also wounded.

Caneri once again assumed command of the PPA, which finished its operations around Ravenna and then went into reserve for four months. With the war almost over, the PPA was given the job of disarming some of the partisans groups, and after moving to Rosegg, a small town near the Yugoslav border, was disbanded in September 1945.