 Flamethrowers have not been in the U.S. arsenal since 1978, when the Department of Defense unilaterally stopped using them ⁠— ⁠the last American infantry flamethrower was the Vietnam-era M9-7.They have been deemed of questionable effectiveness in modern combat.Despite some assertions, they are not generally banned, but as incendiary weapons they are subject to the usage prohibitions described under Protocol III of the Convention on Certain Conventional Weapons.