There’s a lot of people who seem to have a knee-jerk reaction to this “that’s a war crime!!1!”, but it really is not. Incendiary weapons (like thermite, white phosphorus and napalm) are not illegal to use against legitimate military targets, including enemy combatants. It’s only a war crime when it’s used indiscriminately against civilians or in civilian areas.
Lot of misinformation out there on this it seems.