The secret of the Hittites' expansion and superiority lay in the fact that they were the first power to develop the process of smelting iron in large quantities, a method that was probably discovered in about 1400 BC. In a time when everyone used bronze for weapons, iron weaponry gave its possessors a great advantage. Despite that advantage, however, the bulk of the Hittite Army was made up of mounted troops and chariots, from which archers fought. Iron weaponry conferred less of an advantage on those troops, but the Hittite infantry carried iron swords and iron-tipped spears and fought in a phalanx formation.