Why were the Assyrians so successful in building their empire

My facts could be mistaken but believe it or not, a crucial technology; I believe it was in fact the Assyrians, who were the first people to use steel. Steel is stronger and lighter than iron. Nothing fancy; not titanium, or the fictional “adamantium” or what have you, just old fashioned, run-of-the-mill steel. The use of steel more than anything gave them a crucial edge; most of the armies they massacred had their iron weapons destroyed by the Assyrians. HELL NO THEY WERENT THE DEVIL WAS DUH.