Flamethrowers were first used in the First World War. Inflammable liquid was forced through a nozzle under pressure from an inert gas. As it emerged, it was ignited by a spark or a charge, causing a short burst of fire, that can be directed at a target.
Soldiers in the British Army used the portable Ack Pack. It carried 4 gallons of fuel that enabled ten 10-second shots to be fired at a range of about 50 yards. Larger flamethrowers were mounted on tanks or armoured vehicles.