Modern portable flame-thrower was German pre World War 1 invention. Its basic structure in all its simplicity: Three containers, two of them contained fuel and third one had flammable pressurised gas (usually nitrogen). Flame tube connected with hose to containers was used to aim the flame. During World War 2 portable flame-throwers become more common and gained popularity as one of the most feared and hated weapons of battlefield. The weapon was dangerous also those carrying it and had short range when compared to other infantry weapons, but inside its short range it proved brutally effective. It is worth noting that portable flame-throwers were not all-around weapons, but highly specialized weapon type used for reducing fortifications. Their flame would get through even narrowest of portholes or vision slots and for killing of any personnel inside a targeted structure such as bunker or cave its flame did not even to reach its occupants, since it could burn off oxygen and suffocate them. Flame-thrower operators were hated priority targets to enemy soldiers. During World War 2 all major players had portable flame-throwers among weaponry used by their engineer corps. While originally portable flame-thrower was designed as a weapon to be used against fortifications, they could also be used as antitank weapons. Use of portable flame-throwers in Spanish Civil War got also Finnish Army convinced that these weapons could be effectively used against tanks, hence such use was included to their operator training and tactics, but ultimately their antitank-role was limited to defensive use for such situations in which use of flame-throwers could be prepared in beforehand and even then tactics called for at least two flame-throwers to be simultaneously used against enemy tank. Considering this is should not be a surprise that in practice flame-throwers of Finnish Army saw so little use that it is uncertain if they succeeded destroying even single tank. In practice they seem to have retained their role in Finnish use as weapon used for reducing fortifications and storming trenches. Finnish military did not yet have flame-throwers in its inventory when Finnish - Soviet Winter War started in November of 1939, but that was about to change.

(Italian Lanciafiamme Spalleggiabile Modello 35)

PICTURE: Finnish soldier poses with flame-thrower M/40 in Märkälä in July 1941. Phhotographer Military official Tervo. (SA-kuva photo archive, photograph number 24478). CLICK THUMBNAIL TO SEE LARGER PIC (156 KB).

Finnish use: 176 bought from Italy during Winter War. Only 28 of those 176 flame-throwers arrived during that war and the rest after it had already ended. These do not seem to have seen yet any use in Winter War, but did see combat use during Continuation War until de facto replaced with captured Soviet flame-throwers M/41-R in frontline troops.

As mentioned when Winter War started at end of November 1939 Finnish military did not yet have flame-throwers. At the time Germany was still leading the development of this weapon, but because their Molotov-Ribbentrop Pact with Soviet Union during Winter War Germany was unwilling to deliver military equipment to Finland. So, Finnish Army decided to acquire its first flame-throwers from Italy. The Italians had portable flame-throwers in large-scale use (there were in total some 1,500 in total at inventory of Italian Army at year 1940) and were quite willing to do business with Finnish military. As a result Finland bought 176 portable flame-throwers type Lanciafiamme Spalleggiabile Modello 35, which Finnish military named as liekinheitin M/40 (flame-thrower M/40). From those 176 flame-throwers ordered from Italy only 28 arrived during Winter War and likely did not yet see any combat-use during it as there were not exactly trained flame-thrower operators in Finnish Army yet at that point. The remaining 148 flame-throwers M/40 were delivered during the peacetime between Winter War and Continuation War. These flame-throwers were issued to Engineer Battalions of Finnish Army for Continuation War and saw extensive combat use during it.

PICTURE: Flame-thrower M/40 being used in Lappeenranta in July 1941. Apparently staged photograph with "attack" against the bunker being staged with Finnish bunker (quite likely bunker 22a). Photographer Military official Olle Salmi. (SA-kuva photo archive, photograph number 24224). CLICK THUMBNAIL TO SEE LARGER PIC (196 KB).

The main parts of flame-thrower M/40 were:

The fuel tank consists two cylinder shape containers. These were divided by horizontal inner wall to two chambers, from which the upper chamber contained nitrogen gas and lower chamber contained fuel. Hose leading to the flame tube was attached low to right hand side of fuel tank. Nitrogen and fuel filling vents and nitrogen pipe connecting the two cylindrical containers were on top of the fuel tank. Empty fuel tank weighted about 10 kg. Flame tube was obviously the part from which the flame burst out. The basic system used in this flame-thrower was the typical to flame-throwers of that era - nitrogen provided pressure for spraying the fuel and once this was ignited it produced a considerable flame. Earlier Italian flame-throwers had used flint-system for igniting the fuel, but the model delivered to Finland had been originally equipped with a lighter system, which was powered with electricity. This electric lighter could be powered by either with dry batteries (one 18-volt battery, four 4.5-volt batteries connected in series or two 9-volt batteries connected in series) or high-voltage inductor. This powerpack containing batteries or high-voltage inductor was integral part attached to this flame-thrower. In case of electic-powered lighter failing to work, the lighting system was also equipped with secondary system containing special ignition cartridge, which when fired provided ignition flame lasting about two minutes. This ignition flame of two minutes provided by secondary system was somewhat two-edged sword - it was very reliable way of lighting the fuel, but at the same time it also often made the flame-thrower operator more easier to spot.

PICTURE: Finnish Army flame-thrower M/40. Drawing based to those in Finnish military manuals. Colours are the best guess - Finnish "field grey" was probably used, but to what extent is difficult to say. Drawing based to drawings in military manuals. CLICK THUMBNAIL TO SEE LARGER PIC (70 KB).

PICTURE: Flame tube of Finnish Army M/40 flame-thrower. Drawing based to drawings in military manuals. CLICK THUMBNAIL TO SEE LARGER PIC (37 KB).

The fuel tank contained 12 - 12.5 litres of flame-thrower fuel. The nitrogen gas in upper chambers of its containers could be loaded up to pressure of 20 at. According manuals (apparently based on experience) filling of the flame-throwers tanks had to be just before use, because the pressure could leak from the tank if it was storaged too long. The typical way of using portable flame-thrower in combat were short (about 1 second) bursts of flame and in this M/40 proved quite capable - it could do as many as 20 - 30 short bursts with one fill. However range-wise it was not quite as effective. Mainly due to low working pressure of this flame-thrower the maximum range of its flame was only about 20 metres or so, which was mediocre at best when compared to other portable flame-throwers of World War 2 era. Also, as usual with portable flame-throwers weight of the weapon was an issue and slowed movement of the flame-thrower team in combat. Due to weight and location of valves operating of the flame-thrower M/40 demanded crew of two men to operate it.

PICTURE: Flame-thrower operator equipped with flame-thrower M/40 and his assistant seen advancing towards their target. Likely a staged photograph. Photographed by Kim Borg in August of 1941 in Rajakontu. (SA-kuva photo archive, photograph number 39468). CLICK THUMBNAIL TO SEE LARGER PIC (171 KB).

Finnish Army developed improvements for its flame-throwers M/40 during Continuation War. Many of the seals used in it were originally made from leather and proved weak then exposed to heat. Hence Finnish Army replaced them with new seals made from copper-asbestos. However the major improvement introduced by Finnish Army to this flame-thrower was replacing original Italian electric-powered lighter system with a mechanical lighter system with sort of wheel-like flints being used to create a spark needed for ingiting fuel vapours, which set the oil sprayed by the flame-thrower on fire. Finnish flame-thrower operators had noted original Italian electric-powered lighter unrealiable - some of the batteries supplied had been dud to begin with and in general their reliability proved questionable in addition to which electical wiring also problems of its own. This while obtaining special cartridges for secondary lighting system also proved difficult. Hence in summer of 1942 flame-throwers M/40 were gathered from engineer units operating them and many if not all flame-throwers M/40 had new Finnish mechanical lighter system installed in them by autumn of 1942.

War experience of Finnish flame-thrower crews was that Italian flame-throwers M/40 also suffered from problems with structural durablity, hence Finnish flame-thrower crews were less than happy with it. When Continuation War progressed Finnish Army captured Soviet flame-thrower M/41-R in substantial numbers, found it better suited combat duties and altimately used it to de facto replace Italian flame-throwers M/40 in combat unit.

It is noteworthy that the Italians were apparently also not happy with the electic-power lighter system of Lanciafiamme Spalleggiabile Modello 35 either and replaced its batteries with electro-magnetic turbine, which was run by movement of fuel during use of flame-thrower. Later on the Italians also developed Lanciafiamme spaglleggiabile Modello 1940 (which had electric lighter with high-voltage inductor) and Lanciafiamme spaglleggiabile Modello 1941 portable flame-throwers, but none of those was ever acquired by Finnish military.

(Soviet ROKS-2)

PICTURE: Captured flame-thrower M/41R in use of Finnish Army engineers. Photo taken during strike team excercise of Jaeger Engineer Platoon of unknown Engineer Battalion in Aunus / Olonets Carelia at March of 1943. Photographer Kim Borg. (SA-kuva photo archive, photo number 123267). CLICK THUMBNAIL TO SEE LARGER PIC (159 KB).

Finnish use: Finnish Army captured unknown but substantial number of this Soviet flame-thrower and re-issued it to its own troops. What is known these flame-throwers were first captured in September of 1941 and remained in use of flame-thrower platoons of Finnish Engineer Corps until end of World War 2.

During Continuation War Finnish Army captured Soviet ROKS-2 portable flame-throwers, which were later adopted to Finnish use. Apparently the first mentioning of this flame-thrower in Finnish publications is in leaflet Taktisia ym. tietoja vihollisesta N:o 20 (Tactical and other information of the enemy number 20), which is dated 19^th of September 1941. The leaflet suggests that Finnish troops had for the first time faced and captured some ROKS-2 flame-throwers (referred as "flame-thrower rifle" in the leaflet) just recently - hence quite likely in October or September of 1941. What made ROKS-2 unusual among flame-throwers of World War 2 era was that the Soviets had tried to camouflage it as M/91-30 military rifle and a rucksack. Because of this purpose the flame tube was shaped to remind rifle and fuel tanks had been attached to frame made from thin steel plate, which covered them - somewhat hiding their structure. What is known suggests that Finnish military probably captured most of ROKS-2 in year 1941, with smaller number of being captured in year 1942. Finnish Army named these captured flame-throwers as liekinheitin M/41-R (flame-thrower model 1941 Russian) and started re-issuing them to its own Army engineers in summer of 1942. Captured M/41-R flame-throwers remained in combat-use with Finnish Engineer Corps to the end of World War 2.

PICTURE: Soviet ROKS-2 flame-thrower captured by Infantry Regiment 5 of Finnish Army in region of Patajärvi / Padozero in Soviet Carelian in late September of 1941. Photographer Hans Lindh. (SA-kuva photo archive, photo number 51555). CLICK THUMBNAIL TO SEE LARGER PIC (182 KB).

Main parts of M/41-R flame-thrower:

Just as with flame-thrower M/40, also fuel tank of this flame-thrower had two cylindrical vertical containers. However the containers of ROKS-2 were in metal frame and had smaller cylindrical horizontal nitrogen tank under them. Each fuel container had filling valve on top of it. The hose containing fuel tank to flame tube was attached low at right hand side fuel container. Pipe connecting nitrogen tank to fuel tank was at the left-hand side. Back of the fuel containers had tool pouch, which contained tools and spare seals for the flame-thrower. The lighting system contained two special ignition cartridges, which started the flame and could be fired by pulling trigger of the rifle-shaped flame tube. Flame tube that dual-trigger design, with rear trigger launching fuel and front trigger fired ignition cartridge, which set fuel-impregnated tow on fire and the burning tow lighted the fuel when rear trigger was pressed. These special cartridges had been made in cartridge cases of standard Soviet 7.62 mm x 25 Tokarev pistol/submachine gun cartridge. The empty fuel tank weight 8.5 kg. Length of the flame tube was 111 centimetres and it weight about 3.6 kg.

The nitrogen tank placed vertically under the fuel tank contained 1.3 - 1.8 litres of nitrogen gas packed to pressure of 115 at. Using working pressure this high had its ups and downs: The range with Finnish flame-thrower fuel was about 30 metres (with Soviet developed flame-thrower fuel up to 36 - 45 metres), but the high pressure also spent lot of fuel real fast. The weapon could only produce 6 - 8 short (one second) bursts of fire without refill. The nitrogen tank weight some 2.8 kg. Effectiveness of camouflage used with ROKS-2 in real battles was also questionable. The nitrogen tank was not covered by steel frame and hose leading from fuel tank to the flame tube was still in plain view. And once the flame was ignited, the true nature of weapon must have been quite obvious. Like with M/40 also M/41-R demanded crew of two men to operate it.

PICTURE: Flame-thrower M/41-R captured by Finnish Army. Photographed by JTV in Museum Militaria in city of Hämeenlinna. CLICK THUMBNAIL TO SEE LARGER PIC (174 KB).

Equipment kit issued to platoon, which operated M/41R flame-throwers included 40 litre nitrogen bottles pressurised at 150 ak. When re-fill meter was used single 40 litre nitrogen bottle allowed the small nitrogen bottle of this flame-thrower to be refilled 7 or 8 eight times, but if hand-operated pressure-pump was used for refill, it allowed single 40 litre nitrogen bottle to provide up to 30 - 40 refills. However this efficiency came with cost of refill system being more complicated and hence requiring more training.

Soviet M/41-R (ROKS-2) had its own reliability problems. Finnish soldiers noted that the ignition cartridges were reliable, but user error or mechanical problems with firing pin or mouth of flame tube being bent could cause misfire. In addition if left unused for too long fuel impregnated in the tow might evaporate or water might get into it and cause it not setting on fire when needed. If Soviet-manufactured special ignition cartridges were not available, cartridge case of 7.62 x 25 or 9 x 19 cartridge filled with crushed match-heads was found to be a functional replacement.

As noted from the two portable flame-throwers used by Finnish Army Soviet M/41-R proved more reliable and practical than Italian flame-thrower M/40- hence becoming the standard portable flame-thrower for Finnish Army engineers starting second half year 1942. Reasons leading to this decision included that M/41-R was more practical design of the two. While the two flame-thrower designs were relatively close weight-wise and hence for flame-thrower operator to move around with one was cumbersome with either, M/41R was more compact in size and proved more convenient to operate.

PICTURE: Finnish Army flamethrower M/41-R (ROKS-2). Drawing based to drawings of military manuals. CLICK THUMBNAIL TO SEE LARGER PIC (71 KB).

PICTURE: Flame tube of flame-thrower M/41-R. Drawing based to drawings of military manuals. CLICK THUMBNAIL TO SEE LARGER PIC (36 KB).

Captured ROKS-3: The Soviets continued development of their ROKS flamethrowers after ROKS-2. The development work produced ROKS-3, which was performance-wise apparently quite similar to ROKS-2, but easier to mass-produce. This flame-thrower has notably simpler fuel container design with single large tubular vertical fuel container and nitrogen tank attached to it was also placed in vertical position. Not only does ROKS-3 seem to be notably easier and faster to mass-produce than ROKS-2, but due to its far simpler construction was likely to avoid durability issues concerning welded sems, which Finnish Army had spotted with ROKS-2. At the same time ROKS-3 was also slightly (some 1.5 kg) lighter in weight than ROKS-2. While the flame tube of ROKS-3 was very similar to one used with ROKS-2, it featured a cylinder of ten ignition cartridges instead of having only two cartridges. Finnish Army captured small number of ROKS-3 flame-throwers, but it is not known of those captured flame-throwers ever saw use with Finnish Army engineers. Unlike with Italian flame-thrower M/40 and captured Soviet flame-throwers M/41-R (ROKS-2) Finnish military did not produce any sort of manual for ROKS-3, which suggests that they may not have been re-issued or their ROKS-2 compatible parts may have been used as spare parts for existing M/41-R flame-throwers.

PICTURE: ROKS-3 flame-thrower captured by Finnish Army in June of 1943. According original photo caption 13 such flame-throwers were captured from the particular battlefield in Rukajärvi / Rugozero Region in Soviet Carelia. The soldier also has captured PPSh-41 submachine gun hanging on his back. Photographed by Military official P. Jänis. (SA-kuva photo archive, photo number 131383). CLICK THUMBNAIL TO SEE LARGER PIC (154 KB).

Finnish flame-thrower M/44: This is relatively light-weight Finnish World War 2 era flame-thrower, which was designed to be attached into Suomi m/31 submachine gun. The design is also referred as flame-thrower M/Kuusinen due to its inventor, Sergeant M. Kuusinen. It never saw large-scale use, because ending of Continuation War in September halted Finnish military weapons production. More info on this page about experimental Finnish heavy weapons projects.

Finnish Army used portable flame-throwers mainly on time of Continuation War (June of 1941 - September of 1944). As noted there were not yet flame-throwers in use of Finnish Army yet during Winter War (November 1939 - March 1940) or what is known in Lapland War (September of 1944 - April of 1945) either. During Continuation War Finnish Army issued flame-throwers to specific platoons of Engineer Battalions and instead of ordnance materials they were categorised among equipment of Engineer Corps. What is known also suggests that flame-throwers M/40 saw only limited use during early part of Continuation War. Not only were the acquired 176 flame-throwers M/40 not numerous enough to equip Flame-Thrower Platoon for every mobilised Engineer Battalion, but lacking previous experience of flame-throwers both Finnish supply personnel and Army engineers were often unaccustomed to how to handle those or even the basic principles of how to operate one. Hence flame-throwers could be damaged due to incorrect handling already before being issued or they were issued incomplete with missing equipment and not all units of Army engineers had even received training for this new weapon either.

Typical Finnish Continuation War era Engineer Battalion early on had separate Liekinheitin joukkue (Flame-thrower Platoon), which was replaced with Jääkaripioneeri joukkue (Jaeger Engineer Platoon) at September of 1943. As organised before Continuation War Liekinheitin joukkue (Flame-thrower Platoon) had in total 19 men, which included platoon leader, his assistant, five flame-thrower teams (of two men) and two mechanics responsible for maintaining their equipment. Later Jääkaripioneeri joukkue (Jaeger Engineer Platoon) each had six flame-thrower crews (with 2 men in each crew). Each of these platoons had in total 12 flame-throwers in their disposal. While these number may feel strange, having two flame-throwers per crew was essential part of tactics.

Portable flame-throwers carried very limited amount of fuel and pressurised gas and once it run out flame-thrower needed to be taken back of the line for re-fill. Hence the idea was that when flame-thrower crew run out of fuel in their first flame-thrower, they could simply take their second flame-thrower and continue fighting instead of heading back for time-consuming process of refuelling fuel containers and refilling nitrogen tank. With this tactical principle flame-thrower crew had to leave combat only after also their second flame-throwers had run out of fuel. Typically each Continuation War era Finnish Army engineer battalion had one of these platoons, although early in the war there were apparently not enough flame-throwers M/40 and trained operators, due to which some Engineer Battalions had to do without. In general usually platoons of Finnish Army engineers who operated flame-throwers like Finnish engineer units were not used on their own or alone, but were instead subordinated to infantry units to assist their combat activities against enemy fortifications and enemy troops inside those. Due to weight and limited range of portable flame-thrower their operators were highly vulnerable priority targets if spotted by enemy, hence own infantry was needed to protect them from the enemy. Platoons that operated flame-throwers were usually organized as temporary trench-storming parties, structure and equipment of which varied depending situation. Other weapons vitally important for the task of storming trenches included hand grenades and submachine guns. In addition of flame-throwers Army engineers would be used in trench storming and bunker busting to use more specialised explosives such as pole charges and Bangalore torpedoes. While satchel charges were routinely used by both infantry and Army engineers.

PICTURE: Flame-thrower operator equipped with flame-thrower M/40 covered by riflemen while using his flame-throwers against enemy dug-outs (staged). Photographed by Military Official Esko Kangas in July of 1941. (SA-kuva photo archive, photograph number 35358). CLICK THUMBNAIL TO SEE LARGER PIC (234 KB).

Standard flame-thrower equipment kit issued to Flame-thrower Platoon or Jaeger Engineer PLatoon contained:

The whole equipment kit issued to this type of platoon usually required two trucks for transporting it.

Finnish military used two kinds of flame-thrower fuel mixes during World War 2:

Summer-mix:

Winter mix:

Flame-thrower fuel was readily mixed for 50-litre tanks, which were used both for transporting and storing up of flame-thrower fuel in ready-to-use form.

From these two flame-thrower models used by Finnish Army captured Soviet M/41-R proved more durable and notably easier to operate and maintain, which made it more popular among soldiers. Finnish sappers preferred it not only for its better reliability, but also more practical design which also somewhat reduced the chance of being spotted and becoming priority target for the enemy. One one detail, which shows the practical difference in between maintaining the two flame-thrower designs is the total number seals used with each design - Italian M/40 had in total 19 kind of seals used in it, while Soviet M/41-R had only two kind of seals. Hence as Continuation War progressed, Italian M/30 were replaced with captured Soviet M/41-R in combat use in Finnish Army.

PICTURE: Captured flame-thrower M/41-R in use of Finnish Army engineers in training centre of Niinisalo. Photographed by Hedenström in July of 1942. (SA-kuva photo archive, photograph number 96295). CLICK THUMBNAIL TO SEE LARGER PIC (183 KB).

However design of Soviet flame-thrower M/41-R also proved to contain dire safety concern. Unlike often shown in war movies being hit rarely caused flame-thrower to explode into ball of flame, but this very safety concern came with that danger. In case of working pressure in the system of M/41-R falling too much while there was still fuel left flame could get inside the system and reach fuel tanks, which would cause them to explode. Finnish Army noted this happening at least twice - first in February of 1943 in a training course for officers of VI Army Corps and second time in Non-commissioned Officer School of 21^st (Infantry) Brigade in June of 1944. While the safety precautions were added after the first accident, it did not prevent the second accident, both of which were fatal to the flame-thrower operators involved. Due to the second accident all flame-throwers of this model were inspected and more additional instructions were issued. The instructions specified that particular care had to be taken in not releasing pressure from the flame-thrower until the flame was completely out and if any of the valves was leaking, the leaking valve absolutely needed to be replaced before the flame-thrower being taken in use.

Also unlike sometimes seen in war movies Finnish Army limited to use flame-throwers strictly for outdoors only. Flame-throwers do not kill only with their fire. Indoor use would have easily been fatal for flame-thrower operators themselves due to flame burning out oxygen and creating poisonous gasses capable suffocating anybody inside a closed space even if the actual flame would not reach them.

Portable flame-throwers were simultaneously rather clumsy to use and contained delicate components, which could be easily damaged. Hence they required frequent inspections, maintenance and repairs. Smaller repairs could be done in repair shops belonging to units, but for repairs concerning integrity of pressurised containers they were sent to Engineer Depot (Pioneerivarikko), which was also responsible for regular checks of such containers. Pressurised containers that were in use were subject to regular annual check, while stored up containers were checked every two years. 40 litre nitrogen bottles were refilled by private company Gasaccumulator Oy , while oil products needed for summer mix and winter mix used in these flame-throwers were purchased by Finnish Army from variety of commercial enterprises, which included Oy Shell Ab.

SOURCES:

Masters thesis "HUOMIO, TULTA" Suomen puolustuslaitoksen liekinheittimet ja niiden käyttö jatkosodassa ("ATTENTION, FIRE" Flametrhrowers of Finnish military and their use in Continuation War) by Senior Lieutenant Aapo Siltainen (published year 2026).

Military leaflet: Taktisia ym. tietoja vihollisesta N:o 20 (dated 19th of September 1941) (Tactical and other information about the enemy number 20).

Military manual: Aseopas V, liekinheitin (1940) (Weapons manual V, flame thrower).

Military manual: Liekinheitinopas (M/40), (Printed by Otava in 1941) (Flamethrower manual for fllame thrower M/40).

Military manual: Liekinheitinopas, kalustot m/40 ja M/41-R. 4. (Printed 1942) (Flame thrower manual for throwers m/40 and m/41-R).

Jatkosodan historia, part 1 (History of Continuation War, part 1)

Pioneerit sodassa 1939 - 1944, part II (Sappers in War 1939 - 1944, part II)

Brassey’s Infantry Weapons 1950 - 1975

Archive folder T-19187, Finnish National Archives.