Damascus steel was prized for it's ability to produce strong ultra sharp swords. But the recipe was lost in the 1800s. Now it is understood that the steel was produced as crucible steel which permits control of carbon content at lower temperatures though the process takes considerably more time. In addition the iron used to source the steel contained vanadium which is thought to catalyze the formation of iron carbide crystals and also appears to have caused the formation for carbon nanotubes within the steel.
—David Foss