Salaam,
I know that Islam forbids the use of fire as a means of punishment (I have read at least one Hadith to this effect), but are fire-based weapons permitted in war where they may save the lives of Muslim soldiers.
I specifically refer to 3 weapon systems.
1.) Flame-throwers, which are highly effective at killing enemy soldiers who are in bunkers, that would prove otherwise very bloody to attack.
2.) Napalm bombs, which set large areas on fire with petroleum jelly-based flames that cannot be extinguished with water. These are again useful against fortified enemy positions, and apparently some Indian sources I have read have claimed that Pakistan used napalm bombs with great effect in Kashmir in 1965.
3.) Fuel-air bombs, such as the daisy-cutters used by America in Afghanistan (though most fuel air bombs are much smaller). These create a brief firestorm that kills by either sucking all of the air out of your lungs and thus suffocating you if you are towards the edge of their blast radius, or by incinerating you if you are closer to the point of detonation. Fuel air bombs are once more used mainly against fortified enemy positions, and have an extremely large lethal radius (the daisy cutters were 15,000 lbs fuel air bombs that had a blast radius equivalent to a small nuclear explosion.)
All of these weapons kill using fire, which I have seen Hadith prohibit fire as means of punishment. Are they permitted in war, where they are often much more effective weapons than normal explosives, and so are likely to save the lives of Muslim soldiers?