What fuel did the Assyrians use to melt iron?

Assyria is known to us from ancient history for its strong army, which contributed to the establishment of the power of the Assyrians in most of the east in the 8-7 century BC. To build such a strong army required advanced weaponry. At that time, the processing of iron was already known in Assyria; coal was used to melt it. True, Assyria often bought weapons from other countries when there was not enough of its own production.