The advantages of a long, sharp blade in battle had to await advanced smelting and casting technologies before they could be realized. By about 1500 BC the war ax had evolved into the sickle sword, a bronze sword with a curved, concave blade and a straight, thickened handle. Bronze swords with straight blades more than three feet long have been found in Greek grave sites; however, because this length exceeded the tensile strength of bronze, these swords were not practical. As a serious military weapon, the sword had to await the development of ironworking, and the first true swords date from about 1200 BC. Swords in antiquity and classical times tended to be relatively short, at first because they were made of bronze and later because they were rarely called upon to penetrate armor. The blade of the classic Roman stabbing sword, the gladius, was only some two feet long, though in the twilight years of the empire the gladius gave way to the spatha, the long slashing sword of the barbarians and forerunner of the great broadswords of medieval Europe.