Yes, the Geneva convention Protocol III wording is this....
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But I would argue that a thermobaric / F.A.E. isn't really an incendiary device at all. Not like our Napalm in Vietnam, or our fire bombing Dresden Germany. Are we now war criminals??
A thermobaric bomb simply pre-sprays the air with a 'fuel' and then ignites it for a larger explosive blast wave. It's not designed to start fires, it's designed to flatten buildings.
And it's not anything close to even a small atomic bomb. That kind of media hysteria/exaggeration and corny terms like 'vacuum bomb' leads me to think it's some deliberate disinformation campaign.
Our MOAB, the largest conventional bomb is US inventory, the size of a small bus pushed out of a cargo plane, has a yield of 11 tons. The Hiroshima bomb, tiny by modern standards, was 13,000 ton yield ! Modern nukes are in the mega (million) ton range!
Was it the Russian TOS-1A thermobaric Launcher? Hardly a small nuclear weapon. Not by a long shot. I don't want anyone in Ukraine to die, by bullet or bomb (of any type) but dead is dead. And I think exaggerated hysterical media hype is only pushing this further past a point of no return....