Flamethrowers were never completely banned in war, which surprises most people. What happened is more nuanced: international treaties restricted how and where they can be used, and the U.S. military independently retired them from service in 1978 for both ethical and practical reasons. The story involves a combination of humanitarian concern over extreme suffering, battlefield limitations that made the weapons impractical, and international pressure to regulate incendiary weapons broadly.
What International Law Actually Says
The treaty most relevant to flamethrowers is Protocol III of the Convention on Certain Conventional Weapons (CCW), which regulates incendiary weapons. It defines an incendiary weapon as any munition “primarily designed to set fire to objects or to cause burn injury to persons through the action of flame, heat, or combination thereof, produced by a chemical reaction.” Flamethrowers fit squarely within that definition.
Protocol III doesn’t outright prohibit incendiary weapons, though. It restricts their use, particularly against civilian populations and near concentrations of civilians. The protocol’s core concern is limiting what it calls the “indiscriminate and uncontrollable effects of fire as a weapon.” It draws a distinction between air-delivered incendiary weapons, which face tighter restrictions, and ground-based systems like handheld flamethrowers, which are regulated differently. The result is a set of rules that heavily constrain when and where a flamethrower could legally be deployed, but stop short of a total ban.
The International Committee of the Red Cross has gone further in its advocacy, citing the “serious disabilities that are frequently the result of the use of incendiary weapons” as grounds for stronger prohibitions. Under customary international humanitarian law, incendiary weapons are specifically listed among those that cause “superfluous injury or unnecessary suffering,” a legal standard that makes their use in certain contexts a violation of the laws of armed conflict.
What Flamethrowers Actually Do to People
The push to restrict flamethrowers stemmed largely from what happens to people caught in their path. The injuries are not like those from bullets or shrapnel. A flamethrower projects burning fuel, typically gasoline-based or napalm, that sticks to surfaces and continues burning. Temperatures from gasoline fires inside structures ranged between 350°C and 600°C during World War II testing, with peaks reaching 1,000°C.
Direct exposure to the flame killed within about 60 seconds in wartime studies. But death didn’t always come from burns alone. In enclosed spaces like bunkers and tunnels, where flamethrowers were most commonly used, the fire consumed all available oxygen. Researchers found that oxygen was completely depleted for up to 15 seconds at a time, more than enough to cause instantaneous unconsciousness. Carbon monoxide levels spiked to lethal concentrations rapidly. Napalm was particularly dangerous in this regard because it consumed far more oxygen and produced far more carbon monoxide and carbon dioxide than standard fuel.
For those who survived initial exposure, the outcomes were grim. Severe burns covering large portions of the body led to profound shock, organ failure, and infections that were extremely difficult to treat, especially under battlefield conditions. The suffering experienced by burn survivors, both immediate and long-term, became one of the strongest humanitarian arguments for restriction. Many required years of surgeries and rehabilitation, and permanent disfigurement was common.
Why the U.S. Military Stopped Using Them
The United States retired flamethrowers from combat in 1978 through a Department of Defense directive, but the reasons were as much practical as they were ethical. On the battlefield, flamethrowers had serious tactical drawbacks that made them increasingly hard to justify.
The most obvious problem was vulnerability. A soldier carrying a flamethrower wore a heavy fuel tank on their back, which restricted movement and made them an unmistakable target. Every enemy combatant on the field understood what that tank meant, and flamethrower operators drew concentrated fire. The fuel tanks, while not as explosion-prone as movies suggest, still represented a catastrophic risk if punctured by enemy rounds.
Then there was the issue of limited use. A flamethrower provided only about 20 to 30 seconds of total firing time. After those seconds were spent, the operator was carrying a heavy, useless piece of equipment with no offensive capability. In the fast-moving infantry combat that characterized post-World War II conflicts, that tradeoff became harder to accept. By 1978, other weapons could accomplish similar objectives, clearing bunkers, destroying fortified positions, without requiring a soldier to get within 20 to 40 meters of the target while wearing a bullseye on their back.
The Vietnam War and Shifting Public Opinion
Flamethrowers saw extensive use in World War II and the Korean War, primarily for clearing bunkers, tunnels, and fortified positions on Pacific islands and later in Korea’s mountainous terrain. By the Vietnam War, they were still in the arsenal but increasingly controversial. The conflict’s heavy media coverage meant that the realities of incendiary warfare reached civilian audiences in ways they hadn’t before.
The broader use of incendiary weapons in Vietnam, including napalm dropped from aircraft, generated significant public outcry. Flamethrowers were part of that larger conversation about whether weapons designed to burn people alive could ever be justified. The U.S. military sometimes framed flamethrower use in terms that minimized its lethality, arguing that the weapons killed so quickly the victims didn’t suffer. Veterans who operated them often told a different story. The moral weight of using the weapon left lasting psychological marks on many operators, some of whom rarely spoke about their experiences afterward.
Modern Replacements and Legal Gray Areas
The retirement of traditional flamethrowers didn’t eliminate fire-based weapons from the battlefield. Thermobaric weapons, which disperse a fuel cloud and then ignite it to create a massive pressure wave, have largely taken over the tactical role flamethrowers once filled. These weapons are devastatingly effective against enclosed positions and fortifications.
Legally, thermobaric weapons occupy a different category than flamethrowers. Under the CCW’s Protocol III, an incendiary weapon must be “primarily designed to set fire to objects or to cause burn injury.” Thermobaric weapons are primarily designed to generate blast and pressure. The fire and heat they produce are the mechanism for creating that blast, but burns to people are considered an incidental effect rather than the weapon’s primary purpose. This distinction means thermobaric weapons are not classified as incendiary weapons under international law, even though they can cause severe burns and oxygen depletion similar to what flamethrowers produced.
New questions are also emerging as flamethrower technology evolves. Small aerial drones equipped with flamethrower-type devices have appeared in recent conflicts, raising questions about whether Protocol III’s distinction between air-delivered and ground-based incendiary weapons still makes sense. A flamethrower mounted on a small guided drone can be directed precisely throughout an operation, making it arguably more discriminate than a traditional handheld unit, yet its classification under existing treaties remains unsettled.