"Bushido" and the culture of the samurai as most people understand it was more or less invented whole cloth as a romanticized, retroactive mythology[0], well after the cultural relevance of the samurai had passed on. It was embraced by the wartime Imperial government for its propaganda value, but that doesn't mean the government necessarily bought into it.
That was a really interesting read and I think it supports the concept that "Bushido" was in full swing by the 1940's:
Bushido would find its ultimate embodiment in kamikaze pilots and foot-soldiers who “honorably” sacrificed themselves for their country. “Although some Japanese were taken prisoner,” David Powers of BBC writes, “most fought until they were killed or committed suicide.
[0]http://www.tofugu.com/2014/12/08/bushido-way-total-bullshit/