This study examined the mechanical behaviour of the Japanese bo during simulated attack and defence manoeuvres with the aid of finite element analysis. The bo properties varied were handgrip location along the bo shaft and shaft diameter. It was found that an optimal attacking response could be achieved for the following factors: (1) the striking point on the attacking bo, (2) the holding point on the attacking bo, and (3) the diameter of the attacking bo. In addition, the defending response was optimal when defending with an attacking stance. Optimal bimanual grip locations were identified to be in agreement with common practices exhibited by karate practitioners. It was also found that bo geometric construction properties substantially modified the mechanical response. Further empirical testing is needed to verify the finite element analysis findings.