Throughout the ages, civilization have risen and fallen based upon the sophistication of their weaponry. As metalworking became increasingly advanced, weapons became denser and harder. The first great advance in weaponry making occurred during the Bronze Age, when the most advanced metalworking techniques consisted of smelting copper and tin from naturally occurring outcroppings of ore, and then alloying those metals in order to cast bronze. Swords, spearheads, and arrowheads were cast from molten metal and, once cooled, hammered to increase the density. Eventually, after the advent of iron and the coming of the Iron Age, weapons manufactured from this harder metal were able to cut through their softer bronze counterparts. The Iron Age highlighted the impressive advantage gained by those civilizations that had access to superior resources and advance technologies. While many older blade shapes were carried into the Iron Age, the use of iron led to a greater variety of blade types and styles, allowing the sword maker to create weapons that were also works of art.