What happened to flamethrowers? You'd see them in war documentaries about WWII, the Korean War, and Vietnam, but after that they just seemed to disappear. Was there a treaty that deemed them unethical or something or were they just not effective weapons?
Also, most games and media seem to depict flamethrowers as a short-range weapon that just burns everything nearby with a huge flame (like this), but then this image always comes to mind. What were the differences in how these kind of devices worked?
They're not really that useful any more, they were used during the two world wars to empty bunkers and complex emplacements quickly, which was fine and dandy because there wouldn't be civilians about, and killing civilians is what today's forces try their best to avoid. This is a problem because a lot more conflicts are happening in areas where civilians are present, so you can't run in and immolate everyone.
Flamethrowers have crazy ranges when the fuel is viscous enough and propelled with enough force. A liquid fuel on it's own propelled by compressed gas was insufficient and would limit the range, if the liquid was made viscous enough, it would leave the barrel as a consistent stream rather than a spray. The original composition named 'Napalm' was composed of Naptha (a petroleum-derived fuel) and Palmitic acid/Palmates (a fatty acid). Oh, and streams of Napalm were capeable of bouncing off walls and causing further immolation.
They were an effective psychological weapon as well as room-clearing device, fire scares people, and 10+ seconds of literal firehose does a good job of making opponents stuff themselves.
Taking a wild guess here, I'm thinking that they were both unethical and ineffective. In Vietnam with a flamethrower, you could come *this* close to starting a huge forest fire that might destroy your base.
Both points are correct to some degree, burning everyone to death in unholy flames that would stick and cause 2
nd degree burns at minimum is sort of frowned upon these days. That, and whilst 10 seconds of burning horror is more than enough for one emplacement, it's a lot of weight for a pretty small period of use. That, and the compressed contents would spray out and likely ignite if the flamethrower's tanks were shot.