that "the metallographic evidence shows that Polybius was right up to a point. To judge from the swords examined in this survey, only one third could be described as conforming to the quality which he ascribed generally to Celtic swords. Even so, it is quite possible that even some of the better quality swords would have failed in battle." Nevertheless, he argues that the classical sources are exaggerated. Plutarch's claim that Celtic swords would bend completely back is implausible, as only a slight bending would be likely. Pleiner also notes that metallurgical analysis performed on Celtic swords suggests that they were only work hardened and only very few were quench hardened, even though they frequently contain enough carbon to be hardened (in particular the swords made from Noric steel). Quench hardening takes the full advantage of the potential hardness of the steel, but leaves it brittle, prone to breaking. Quite probably this is because tempering wasn't known. Tempering is heating the steel at a lower temperature after quenching to remove the brittleness, while keeping most of the hardness. There is other evidence of long-bladed swords bending during battle from later periods. The Icelandic Eyrbyggja saga, describes a warrior straightening his twisted sword underfoot in a manner similar to Polybius's account: "whenever he struck a shield, his ornamented sword would bend, and he had to put his foot on it to straighten it out". Peirce and Oakeshott in Swords of the Viking Age note that the potential for bending may have been built in to avoid shattering, writing that "a bending failure offers a better chance of survival for the sword's wielder than the breaking of the blade...there was a need to build a fail-safe into the construction of a sword to favor bending over breaking". See also Pattern welding Bronze Age sword Early Iron Age Noric steel Spatha Migration Period sword Celtic warfare Asi (sword) Khanda (sword) References Literature C. R. Cartwright, Janet Lang, British Iron Age Swords And Scabbards, British Museum Press (2006), . Andrew Lang, Celtic Sword Blades, in Man, Royal Anthropological Institute of Great Britain and Ireland (1907). J. M. de Navarro, The Finds from the Site of La Tène: Volume I: Scabbards and the Swords Found in Them, London: The British Academy, Oxford University Press (1972). Radomir Pleiner, The Celtic Sword, Oxford: Clarendon Press (1993). Graham Webster, A Late Celtic Sword-Belt with a Ring and Button