The Flamethrower brought terror to French and British soldiers when the German first used them in 1914 and 1915. The German's tested two versions of the Flamethrowers both of which were made by Richard Fielder. The smaller version they tested was the Kleinflammenwerfer. It was designed for portable use. A single man was meant to carry it. The Kleinflammenwerfer used pressurized air and carbon dioxide/nitrogen and shot a stream of burning oil that could shoot 18 meters.
This is the smaller flamethrower: The Kleinflammenwerfer.
Fielder's second design and larger model worked along the same lines but wasn't suitable for a single person. This design was called the Grossflammenwerfer. Even though you needed more than one person to carry the Grossflammenwerfer, it had a maximum range that was twice that of the Kleinflammenwerfer. Also, it could sustain flames for 40 seconds which was very impressive back then. A con was that the fuel was very expensive.
This is the Grossflammenwerfer.
The first notable use of the Flammenwefer in WWI came in a surprise attack on the British at Hooge in Flanders. This attack happened on July 30, 1915. The result of the two day fight the British lost 31 officers and 751 other people during the attack due to the Flamethrowers.
This is a photo of the smoke that came from the Flamethrowers due to the fire burning trees and vegetation.
After the success of the Hooge attack the Germany army adopted the use of Flamethrowers. They were intended to be used in groups of six during battle. Two soldiers manned each Flammenwerfer. The main purpose of the Flammenwerfers were to push back enemy lines at the beginning of a German attack.
After the many attacks from the Flamethrowers the Britians experimented with their own models. To prepare for the Somme offensive they constructed four models. Each model weighed two tons and had a range of 90 yards. The Britians build them directly into a trench in No Man's Land and was 60 yards from the German's line. Each flamethrower was built piece by piece and two were destroyed by shellfire before the start of the Somme offensive. The remaining two were used but were only effective at clearing nearby trenches.
Here's an example of a trench Flamethrower.
The French also developed their own one-man Schilt flamethower. It was a superior to the German model. The French used the Schilt flamethrowers in trench attacks during 1917 and 1918. To answer back to the French and British Flamethrowers the Germans produced a lightweight version of their Flammenwerfer that had the ability of self igniting. The Germans named this Flamethrower the Wex.
This is an image of three soldiers holding up a Schilt flamethrower.
This is an image of a Wex flamethrower being carried on a person's back.
During WWl the Germans launched 650 flamethrower attacks and it is unknown how many French and British attacks there were. Flamethrowers were still used in WWll. It was very common for tanks to have flamethrowers attached to them.
This is a M4 Sherman Flame Thrower Tank that was used in WWll.
In WWll Americans used flamethrowers to clear Japanese trenches and bunker complexes. In a case that the Japanese were deep in caves Americans would use the Flamethrowers to consume the oxygen and suffocate the occupants. Flamethrowers were also used in the Normandy Landings to clear Axis fortifications.
The United States Department of Defense decided to stop using flamethrowers in 1978. Flamethrowers have been removed from the United States weapons arsenal and are not currently used by any American soldiers.
Sources: http://www.firstworldwar.com/weaponry/flamethrowers.htm https://en.wikipedia.org/wiki/Flamethrower https://www.thebalance.com/flamethrowers-one-of-the-most-controversial-weapons-3345070