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WW2 Yugoslav Partisan Armor of Western Origin

Light Tank M3A3 with 2 cm Flakvierling 38

Yugoslav Partisans (1944)
Improvised Self-Propelled Anti-Aircraft Gun – 2 Converted

During the Second World War, the Yugoslav communist Partisans were often faced with shortages of war materiel. They were especially lacking in regards to armored vehicles and tanks. Luckily for them, after 1943, the Western Allies decided to send large quantities of all kinds of war materiel, including M3A1/A3 light tanks. These tanks were a welcome addition to the Partisan’s fight for the liberation of occupied Yugoslavia. By the end of 1944, the Partisans mounted captured German Flakvierling 38 anti-aircraft guns on two M3A3 tanks. What they actually intended with these vehicles is unclear, as the enemy air force was almost non-existing by this late stage of the war.

The modified M3A3 armed with the 2 cm Flakvierling 38 anti-aircraft gun. Source: D. Predoević Oklopna vozila i oklopne postrojbe u drugom svjetskom ratu u Hrvatsk

The M3 light tanks in the Balkans 

Following the quick conquest of the Kingdom of Yugoslavia during the April War, which lasted from 6th to 18th April 1941, its territories were divided between the victorious Axis forces. Due to the harsh and brutal occupation by the Axis troops stationed in Yugoslavia, by the second half of 1941, two resistance groups started a rebellion against the occupiers. These were the Royalist Chetniks and Communist Partisans. Although, in the beginning, these two groups worked together in the fight against the occupying Axis forces, a conflict between these two forces in late 1941 would break out into open civil war. This lasted until the end of the war and the victory of the Partisans.

By the end of 1943 and the start of 1944, the Communist Partisan movements were heavily involved in organizing a number of attacks on the Germans and their allies, especially vital communication and supply lines, military bases, and airfields, inflicting increasing losses in men and materials. While, initially, the Western Allies mainly supported the Chetnik movement, due to various reasons (including a lack of major military action against the Germans or even open cooperation with them), this attitude changed drastically from 1943 onwards. The Allies instead focused on supporting the ever-increasing Partisan movement by supplying them with ammunition and equipment but also special personnel to help train the Partisan ground forces.

Beside these, the Allied High Command made an agreement with the leader of the Partisans, Josip Broz Tito, to form a tank brigade that was to be equipped with Allied tanks and armored cars. The unit, named the First Tank Brigade, would be formed on 16th July 1944. The British supplied some 56 M3A1/A3 tanks, 24 AEC Mk.II armored cars and two M3A1 scout cars. The Partisan crews were previously sent to Italy in order to be trained in operating these vehicles. They also managed to salvage a few more damaged tanks from Allied repair facilities.

A Partisan M3A3, easily recognizable due to the large Yugoslav flag (with the added Red star) usually painted on the tank’s sides. Source: Wiki

The First Tank Brigade would see extensive action against the Germans and their allies until the end of the war in May 1945. Due to a high attrition rate, a great number of  M3A1/A3 tanks were either lost or heavily damaged. Given the general lack of replacements, these had to be repaired in order to keep the whole unit operational. Some damaged vehicles had their turrets removed and replaced with captured weapons. One such modification included installing a captured 2 cm  Flakvierling 38 on top of an M3A3 tank, creating a bizarre vehicle somewhat similar to the German Wirbelwind.

The M3 Light Tank

The M3 Light Tank was designed in 1940 to replace the older and outdated M2 tanks that were in service with the American armored forces. The M3 had many improvements over the M2, including thicker armor, stronger (due to the increase in weight) vertical volute spring suspension (VVSS) with a bigger rear idler wheel, increased speed, and improved firepower consisting of four 7.62 mm machine guns and a 3.7 cm cannon. The first series was powered by the gasoline-fueled (petrol) Continental seven-cylinder four-cycle radial aircraft engine. After 1942, a new four-stroke diesel radial Guiberson A-1020 engine was used. It had a crew of four (driver, driver assistant, gunner, and commander). From March 1941 to August 1942, some 5,811 Stuarts with petrol engines and 1,285 with diesel engines were built. The much improved M3A1 version was produced from April 1942 onwards. The first batches of M3A1 tanks were built by using riveted armor, but later models had welded armor. The changes that were made were an improved turret design (the small commander cupola was removed) with two hatches, reducing the number of machine guns to three on later built vehicles, and the addition of a turret basket.

Shortly after the M3A1, a new model, the M3A3, was made as a result of the poorly designed frontal armor and small fuel capacity of the first versions. The front and side armor of the Stuart M3A3 were angled and the front hatches for the driver and his assistant were replaced by new overhead ones. Due to the extra space that the Stuart M3A3 now had, it was possible to increase the fuel capacity. This version was produced until August 1943, with a total of some 3,427 vehicles being built.

The M3A3 light tank. Source: https://warspot.net/118-light-tank-m3a3-american-emigrant

The Stuart series saw extensive operational service throughout the war on many different fronts. The USA supplied the Stuart series to other nations through Lend-Lease, including the British Empire, USSR, Brazil, China, France, the Netherlands, and many other Latin American nations. Britain would subsequently give some of their Stuarts to the Yugoslav Partisans. By 1943, however, the M3 was already outdated, due to its weak gun and feeble armor.

Repair facilities at Šibenik

The Partisan First Tank Brigade, after some heavy fighting with the Germans, managed to push them out of the city of Šibenik (located on the Adriatic coast of modern Croatia), which was captured on 3rd November 1944. Prior to the war, Šibenik had been a large naval shipyard and possessed a number of workshops. Despite many of them being sabotaged by the retreating Germans, there was still sufficient working equipment and materials left to meet the needs of the Partisan mechanics, who were somewhat in great need of such tools. Namely, the fighting with the Germans had led to heavy tank losses. As there was no way to replenish lost tanks, the Partisans were forced to try to salvage and repair damaged vehicles. Even those that were damaged beyond repair were reused for spare parts. Enemy vehicles and equipment captured by that time were also transported to Šibenik in hope of repairing them or, if this was not possible, to be cannibalized for spare parts. Šibenik would remain the Partisans’ main base for repairs and maintenance until the end of the war. In addition, it also served as a vital training ground for new Partisan tank crews from November 1944 onwards. The Partisan repair work was actually supervised and assisted by British Major Peterson supported by an unnamed Sergeant.

Modification of the M3A3  

While the Partisans were surely grateful to the Allies for the Stuart tanks, they were, to say the least, quite disappointed with their firepower. The Stuart was armed with a 37 mm gun, which was quite inadequate for either anti-tank or assaulting fortified enemy positions. By the end of 1944, at the ‘La Dalmatien’ workshop in Šibenik, a number of Stuarts with damaged turrets that were probably beyond repair were present. A decision was made by the Partisan authorities stationed in Šibenik to try and install a number of German captured weapons on the Stuarts in the hope of increasing their combat effectiveness. The lack of anti-tank firepower was somewhat resolved by installing a 7.5 cm PaK 40 anti-tank gun on a few modified M3A3 chassis. It is not clear why, but on two vehicles, the effective 2 cm Flakvierling 38 anti-aircraft gun was installed. They could have converted these two chassis in the same manner as the previously mentioned anti-tank version, as they had a number of supplied 5.7 cm (6-pounder) and captured 7.5 cm PaK 40 anti-tank guns in use. Given the fact that the use of German aircraft in Yugoslavia by late 1944 was rare at best, coupled with the total Allied air support, it seems quite unreasonable to build vehicles to counter this inexistent threat of enemy air attack. Sadly, due to a lack of information in the sources, no valid conclusion can be made as to why this conversion was done. It is also possible that the Partisans used what they had available at that time.

The 7.5 cm PaK 40 anti-tank version of the M3A3 employed by the Partisans near the end of the war. Source: www.srpskioklop.paluba.info

General information about these two vehicles is scarce and difficult to find, mainly as the Partisans kept a poor record of them. What is known is that these were likely hasty improvisations with little to no testing done prior to their completion. The work on these modifications began sometime at the end of 1944 and was completed by early 1945.

Name?

Sadly, there are no available sources that mention the name of these vehicles. It is also unknown if the Partisans ever actually bothered to give them any designation or even a nickname. Sometimes, it is simply referred to as the  2 cm Flakvierling 38 on M3 Stuart. This article will use the simple Flak Stuart designation for the sake of simplicity only. It is important to note that this is purely a modern designation.

The Modifications

Installation of the Gun

Due to a general lack of information, how the Partisans actually mounted the 2 cm Flakvierling 38 anti-aircraft gun is not known. But, unlike the PaK armed Stuarts, the Flak version had a much simpler construction. It is highly likely that the Partisans simply placed the gun on top of the M3A3 and connected it to the chassis top, possibly using bolts or even simply welding. While welding it to the chassis was easier, it would mean that the gun could not be easily removed, so this seems unlikely but possible. If the Partisans even covered the opening left by the removal of the turret is also sadly unknown.

Armament

This vehicle was armed with the 2 cm Flakvierling 38 anti-aircraft gun. A well-known anti-aircraft gun of the Second World War, it was designed by Mauser-Werke to replace the older 2 cm Flak 20, and was introduced in May 1940. While initially issued for the use in the Kriegsmarine (German Navy), it would be allocated (both in towed and or mounted on various vehicles, like tanks or half-tracks) to field troop use and some 3,850 such guns would be built. Its effective firing range was between 2 to 2.2 km, while the maximum horizontal range was 5,782 m. The maximum rate of fire was 1,680 to 1,920 rpm, but 700-800 rpm was a more appropriate operational rate of fire.

The 2 cm Flakvierling 38. Source: weaponsystems

Unlike the PaK Stuart, which incorporated a number of changes and modifications, the Flak Stuart’s main weapon was simply placed on top of the chassis. While there is no information in the sources, it is highly likely that the overall characteristics of the main gun were unchanged. The gun could traverse a full circle, while the elevation was –10° to +100°. The 2 cm Flakvierling 38 was fed by 20 round magazines. The gun itself had a special ammunition box in its base (on both sides), where up to 8 magazines could be stored and which were on easy reach by the two loaders. This means that at least 320 rounds could be carried with the vehicle. Due to these magazines being relatively small, additional spares could be carried inside the vehicle or stored somewhere on the superstructure. On the other hand, given that this was a captured weapon, the only way to acquire additional spare ammunition was by capturing it from the enemy. This means that, if the Flak Stuart crew used the gun too often, there is a possibility that they may have depleted the available ammunition reserves quickly before replacements could be captured. This also meant that the total ammunition load could be limited by what they had on hand. Secondary armament consisted of the original hull-mounted Browning 7.62 mm machine gun and the crew’s personal weapons.

A side view of the 2 cm Flakvierling 38, note the 7 magazines placed on the bottom of the gun mount. Source:en.topwar.ru

Armor Protection 

The Flak Stuart did not receive any major modification regarding its overall armor protection. The hull armor remained the same. The only protection for the gun operators was the gun shield that provided only limited protection in front of them. This meant that the gun operators were almost completely exposed to enemy return fire of nearly all calibers. Using this vehicle in close combat, such as in cities, would be very dangerous for the crew.

While the modified M3A3 had a simple overall construction, its crew was almost completely exposed. Source: www.reddit.com

Crew Hatches

The removal of the turret was not the only change to the Flak Stuart. It was noted (even on the unchanged M3A3 tanks) that, if the main gun was placed above the crew hatches, it could prevent them from opening them. For this reason, the Partisan engineers simply modified the two hatches, which now opened forwards. This provided the gun with a better firing angle but also prevented the hull crewmen from being stuck in the vehicle in case of an emergency. The PaK armed version did not receive this modification.

The Flak armed Stuarts had their front crew hatches modified to be opened forwards. Source: www.srpskioklop.paluba.info
The PaK armed version did not receive this modification, as it was not needed. The gun was sufficiently high up that these could be opened with any problem. Also note the large plate that is placed in front of the gun. Source: www.paluba.info

Crew

In order to effectively operate this vehicle’s main gun, the gun crew had to consist of a minimum of three members. This consisted of the gunner, positioned in the center, and two loaders placed on either side of the gun. These crew members were placed on top of the superstructure. Besides these, inside the M3A3, on the left side, was the driver. On the opposite side, the assistant driver was responsible for operating the hull-mounted machine gun.

In Combat

While the precise number of PaK Stuarts built is not clear, there is general consensus in the sources that two Flak Stuarts were constructed by the Partisans. The general usage of the two vehicles is unknown. While there are a few photographs of them being used by the Partisans, if they actually saw combat is not clear. Author D. Predoević (Oklopna vozila i oklopne postrojbe u drugom svjetskom ratu u Hrvatskoj) says that, besides a brief mention of the Flak Stuarts near the city of Knin during November 1944, no written document about their use is known.

There is a potential short reference of the Flak Stuart made by authors J. Popović, M. Lolić and B. Latas (Stvarnost): “…. This Tonković, in the fall of 1944, had the entire Corps placed in the aluminum factory buildings in Lozovac. He then informed the Partisans, who arrived with British-supplied tanks and then began blocking the factory. Captain Tonković went through the gate, and when the first tank arrived, he put a Partisan hat with a bloody five-pointed star on his head, entered the tank and began the attack with flak’s…” 

The British tanks mentioned in these sources must be the Stuart tanks, as no other such vehicle was supplied to the Partisans. The reference to using Flak probably refers to the Flak Stuart tank. While the First Tank Brigade had a number of towed Flak guns, the mentioning of a tank attack indicated that this was actually a Flak Stuart. Sadly, the source does not go into more detail about the Partisan tanks.

Author B. B. Dimitrijević (Modernizacija i Intervencija Jugoslovenske Oklopne Jedinice 1945-2006) mentions that these two vehicles did survive the war. In June 1946, the First Tank Brigade handed these two vehicles over to the newly formed First Tank Division. These vehicles were in use until 1949, but because of the fact that some Stuart tanks remained in storage until 1960 or so, it is possible that they were in use even after 1949. Sadly, their final fate is unknown, but they do not seem to have survived to this day.

There are few photographs of the Flak Stuarts being used by the Partisans. If they actually saw combat is not clear. Source:www.srpskioklop.paluba.info

Conclusion

The M3A3 armed with the 2 cm Flakvierling 38 is a quite mysterious modification. While the whole construction was simple, the general reasoning behind choosing this weapon is difficult to fathom. While the 2 cm Flakvierling 38 had a tremendous firing rate and could saturate a target with hundreds of rounds, individually, these were quite weaker than the original 37 mm round. If they wanted to increase the firepower, the Partisans could have simply added anti-tank guns on these two vehicles. Using them as mobile anti-aircraft vehicles may have been a good idea earlier in the war, but by this stage, the German Air Force was almost destroyed. Nevertheless, regardless of its initial intent, the Flak Stuart served as a reminder of the ingenuity of the Partisan engineers by the end of the war.

illustration of the M3A3 Flakvierling
Illustration of the M3A3 Flakvierling by Tank Encyclopedia’s own David Bocquelet

Specifications

Crew 5 (Gunner/commander, two loaders, driver and driver assistance).
Armament 2 cm Flakvierling 38
Engine Continental 7 cylinder petrol 250 hp, air cooled
Armor 13 to 51 mm

 

Sources

 

One reply on “Light Tank M3A3 with 2 cm Flakvierling 38”

Although the air threat was negligable, a multi-barrelled anti-aircraft weapon is very useful for shifting infantry out of the trenches! I should imagine that they were probably used in a close-support role.

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