mechanical incendiary device designed to project a long controllable stream of fire

A flamethrower is a device used to shoot fire. They have been used by the military since the days of Greek fire. Most modern military flamethrowers project flaming liquids.

A soldier using a flamethrower in the Vietnam War

Flamethrowers became rare in the 19th century, due to improvements in other weapons. Trench warfare made them more useful again, and the German army began using them in 1915,