The crew-portable flamethrower came into prominence on the modern battlefield in World War 1 (1914-1918), intended to break the stalemate of Trench Warfare and inflict horrible physical and psychological trauma upon the enemy. The German Army first unveiled use of the flamethrower in war during 1914 in fighting against the French in the Argonne and, on a wider scale, in the 1916 Battle of Verdun. By the time of World War 2 (1939-1945), the class of weapon was still in use, only refined to become a man-portable system with greater range and increased lethality. While the type proved excellent for US personnel in the Pacific Theater when attempting to root out fanatic Japanese defenders, the flamethrower was also used to an extent in the European Theater. For clearing out fortifications with minimal loss to the attacker, the flamethrower was a proven weapon.
The expanding German Army of the 1930s under Adolf Hitler's leadership adopted the Flammenwerfer 35 in 1935 - the word literally translating to "flame thrower" or "flame projector". The weapon was an entire system consisting of the projector with igniter, fuel line and fuel canisters. The dual-canister arrangement was worn as a backpack held up by shoulder straps while the projector assembly was held with two hands as a basic service rifle. This precluded use by the operator of a viable secondary weapon - limited to perhaps a pistol sidearm or dagger. The twin-tank arrangement included a canister filled with 3 gallons of a gasoline/tar compound to serve as the fuel proper and the other canister containing the nitrogen to serve as the propellant. Ignition was via a hydrogen arrangement which eventually proved limiting in severe winter weather (a change to a cartridge system was ordered for subsequent designs such as the FmW 41). The FmW 35 held a useful range out to 25 meters with a 30 meter maximum from the point of the projector, reaching out some 80+ feet, while the hydrogen ignition allowed for some 10 seconds of continuous streaming. When fired into confined spaces such as enemy pillboxes, the flames took on an even deadlier expanded role than the basic stream. The operator was also free to "lay" down fire over an embedded enemy by arching the stream behind defensive walls. The entire FmW 35 system weighed 80lbs and required special training for maximum efficiency. Despite its size and limitations, the FmW 35 series proved a vast upgrade to the larger and heavier three-man systems fielded by the German Army in World War 1.
An inhumane weapon at its core, flamethrowers no doubt were able to fulfill their battlefield roles in a "kill-or-be-killed" environment. Conversely, operators managing their flamethrowers became wholly obvious to enemy snipers and a well-placed direct strike to the canisters would render them useful, the exiting pressures sending the operator falling forward (spraying fuel could ignite in the right circumstances - say with use of incendiary rounds - but not how Hollywood would have you believe). To partially remedy this threat from long range spotters, projectors were modified to appear as though standard service rifles. It is unknown the extent that this deception succeeded. It was common for flamethrower operators to be protected by nearby infantry personnel for obvious reasons - the flamethrower was a specialist unit to be sure.
The FmW 35 series was in standardized use up until 1941 to which the improved and refined Flammenwerfer 41 was then introduced. The FmW 41 incorporated a much lighter, more portable design and improved on the original in several ways including a later adoption of cartridge ignition. Production of the FmW 35 itself spanned into 1941 before attention shifted to the FmW 41 series. The interim "FmW 40" was yet another German flamethrower of World War 2 and appeared in a "life buoy" backpack form but did not see large scale issue nor manufacture.
Flammenwerfer 35 systems were still in use at Stalingrad during the Eastern Front offensives against the Soviet Union.