The Japanese were excessively trained into the WWI model of fighting, but that was not just due to Bushido. Some forms of Bushido do encourage the 1v1 idea, but many dispense with it in favor of effective cooperative fighting. The 1v1 stuff almost lost them Japan when the Mongols first invaded and the Japanese adapted, to a degree, based on that. Only 10 years later the second Mongol invasion attempt faced a much nastier group of Japanese warriors.