This study investigates how spatiotemporal conditions of interpersonal distance and timing in movement initiations influenced decision-making and actions for offence and defense in kendo. We also intend to present verifiable data on the problem of how two players separate from tsubazeriai in matches. Participants were top level players in Japanese university kendo clubs. In the experiment, participants were either given the role of “the first player”, who initiates movements, or “the second player”, who initiates movements after the first. The participants performed each trial as if in a real match from distances of 150, 175, 200, 225, 250, and 275 cm. We analyzed two trends in their decision-making and actions, one of which was the “ease of active striking,” meaning that they were able to initiate movements from a strike rather than defense in each trial. The other trend was the “ease of striking”, meaning participants could strike in each trial and were not only confined to defense. The results showed that it was easier for the first players than the second players with regards to “ease of active striking” and “ease of striking”. In both results, the differences between the first and the second players were extremely clear at a distance of 150 cm and were very clear at 175 to 250 cm distances and almost disappeared at 275 cm. In total, the first players also had a greater frequency of striking success (ippon) than the second players. These results indicated that movement initiation distance and timing changed reaction and movement times in both offence and defense, and also changed the degree to which the first and the second players’ decision-making and actions gave them an advantage. This is because the reaction and movement times required for offence and defense became shorter if the two players were closer to each other. In addition, the first players’ active movements caused the second players to react passively making it easier for the first players to initiate an attack.. Therefore, at close distances, offence became easier while defense became more difficult, and the first players gained a advantage while the second players were placed at a disadvantage. It can be concluded that the first players gain an advantage and the second players become disadvantaged in terms of offence when they are at close distances of 150 to 250 cm. These findings should be useful in combat sports such as kendo for the coaching of decision-making and actions, as well as for making the rules fairer on offense and defense.
