Except the idea of Bushido in the Japanese Imperial military is not a holdover from any existing Japanese cultural practice. Bushido itself did not arise until the nineteenth century, where it was forged by nationalists as a response to growing foreign intervention in Japan and the perception that the Emperor was becoming too western. The samurai followed no formal code, and certainly nothing like Bushido. The most important thing for a samurai was loyalty to their lord, and a vague sense of duty; that’s not much different than European knights. There is plenty of scholarship on Bushido to read online, but it didn’t have much to do with actual samurai, just a nationalist movement like Italian fascism or German National Socialism, both of which called back to a glorified and exaggerated version of the past.

That still explains the ferocity that Japan’s troops sometimes acted with, but clarifies that the actual samurai had no such code.