PC: early incendiary weapons become widespread in western Eurasia before gunpowder?

As the title says, could Greek Fire be more widespread in the Mediterranean basin? AFAIK, its apogee as a thermal weapon happened in the 9th to 11th centuries in Byzantium, and was actually more used for naval engagements than land battles. In spite of its (almost) legendary status as a state secret among the Byzantines, nowadays we know that the Muslims used (in minor scale) a form of combustive weapon with naphta, which might or not be the same Greek Fire.

Now, could these thermal weapons have become more widespread in the High Middle Ages? Perhaps not coming from the Byzantines, but by the more frequent European contact with the Muslims during the Crusades? Were the materials (saltpeter and naphta, for example) readily available to European polities?
 
Incendiary weapon is or was useful against enemy with great concentration. It was useful in ancient naval battles, because combatants had nowhere to run. On the land, its usefulness was low. It was hard to use incendiary weapons against cavalry. Plus, it was expensive to build and maintain.

Unless Muslim built a range of mega cities (like 50k each) among the Mediterranean sea, I can't see military would be interested in them.
 
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