The shape of the Japanese tsuba evolved in parallel with Japanese swordsmithing and Japanese swordsmanship. As Japanese swordsmiths acquired the ability to achieve an extremely hard edge, Japanese swordsmanship evolved to protect the edge against chipping, notching, and breakage by parrying with the sides or backs of swords, avoiding edge-to-edge contact. This in turn resulted in the need to protect the sword hand from a sliding blade in parries on the sides and backs, i.e., parts of the blade other than the edge side, forming the rationale behind the Japanese styled tsuba, which protrudes from the blade in every direction.