In the name of 'historical accuracy', which is kind of a relative term regarding some of CA's releases, I dont think it every really happened that way.
In the samauri culture the worst possible thing that could happen was to be taken as a POW. It is a loss of honor and face. Most samauri would much rather die gloriously on the field of battle. This mindset carried all the way to World War II, which is part of the reason that Truman decided to nuke the Japanese homelands.
Also to be put up against their Diamyo in that fashion would be inconcievable to a samauri. Its almost blackmail or bribery. This political gamesmanship was not common in Japanese feudal society. It is mostly a trait of European kingdoms. To a Diamyo, and especially the Shogun himself, those sort of underhanded actions were not honorable at all.
Bookmarks