As World War I bogged down in the trenches, each side sought a means of breaking the stalemate. Germany’s first attempt was a weapon developed in secret more than a decade earlier.
In 1901 Richard Fiedler rolled out a prototype of what he called a Flammenwerfer (“flamethrower”). Fiedler’s early design centered on a vertical tank divided into two compartments. The lower section held compressed gas, usually nitrogen, which forced flammable oil from the upper section through a rubber tube and past a simple ignition device in the steel nozzle. A stationary form of the weapon, the grosse Flammenwerfer, or Grof, was capable of throwing fire as far as 120 feet. Its smaller cousin the kleine Flammenwerfer, or Kleif, could project flames only half as far but was portable, small enough to be operated by two men.
The German army adopted the Kleif in 1906, and by 1912 the Guard Reserve Pioneer Regiment boasted its own regiment of Flammenwerfer troops. The weapon and its units largely remained a secret, however, until the Germans finally unleashed it at Verdun on Feb. 26, 1915. Shaking off their initial terror, the French counterattacked, retook the lost ground and managed to capture a Kleif, which its weapons researchers promptly disassembled.
At the Second Battle of Ypres, a half-dozen Kleif operators so terrified British soldiers on the night of July 29–30, 1915, that the Germans were able to capture several trench lines. But its material effectiveness seldom exceeded its psychological effect, as the fuel lacked a thickening agent to make it stick to its target—a shortcoming remedied by World War II. Regardless, the Allies soon developed their own versions of the weapon, canceling out what little advantage the Flammenwerfer had briefly granted its inventors.