Iron became increasingly common from the 13th century BC. Before that the use of swords was less frequent. The iron was not quench-hardened although often containing sufficient carbon, but work-hardened like bronze by hammering. This made them comparable or only slightly better in terms of strength and hardness to bronze swords. They could still bend during use rather than spring back into shape. But the easier production, and the better availability of the raw material for the first time permitted the equipment of entire armies with metal weapons, though Bronze Age Egyptian armies were sometimes fully equipped with bronze weapons.