I’ve read a few books recently about dueling and the cultural aspects of its practice in the United States, Europe and Japan.
One aspect of dueling that those books failed to address was when, if at all, a merciful death stroke should be delivered to a defeated and mortally wounded yet conscious and suffering opponent. Was such an act expected or even required in certain situations/cultures? If so, who made the determination - the duelists themselves? The duelists’ seconds?
I’ve never heard of it specifically in the context of duels… actually, I’d expect it to be needed less often in a formal duel (where some sort of medical assistance would often have been arranged for) than in the setting in which I’ve seen mention of it, which was the aftermath of battles. A mercy killing wouldn’t be something you “arrange for”, it’s something you hope won’t be needed.
Hmm… I can’t say for sure, but I’d be willing to conjecture they likely had such a thing in Japan. My inkling comes from the fact that in seppuku (ritual suicide), the disgraced person would have a “second” that would stand behind them and lop their head off just in case cutting their abdomen open left them writhing in agony and not instantly dead (or unconscious leading to dead). I wouldn’t be surprised if there was a similar mercy kill if you lost in a duel.