All sides made use of the flamethrower in World War Two. The portable incendiary device allows the operator to expel a long stream of controllable flame. The first use in World War Two was by the Germans in their invasion of Poland. The flamethrower was also used against fixed fortifications in the subsequent invasions of Holland and France. Germany later adapted vehicles known as Flammpanzers to be used as mobile flamethrowers.
This video shows American engineers demonstrating the use of flamethrowers against a dummy pillbox. The U.S. Marines used flamethrowers extensively in the Pacific to clear Japanese trenches and bunkers. In some cases, where the Japanese fighters were hiding in caves, the flames would consume all the available oxygen causing the occupants to suffocate to death.