You originally stated knives were never a big thing in warfare. You didn't say non-special operations warfare, you did bring up "melee" ......
PRIMARY weapon.
OR weapon of choice
Spears/clubs/and mixtures of this where in heavy use.
Shortswords roman empire (used together with shieldwalls)
(reason i refer to theese is because theese where weapons for "face to face" over long period of times. People back then where as smart as todays people so we have a very long period of time things where tested out.
Then, it was about a very specific situation (bad guy jumps you from hiding) so not you sneaking up to someone but someone sneaking up to you.
Then, what knife would be best for such an situation.
Obvious the one you have on you. DUH.
IF you have an choice about that the longer, the pointier, the better
NOT an "tactical" or "combat" knife made for cutting.
Where single edged shortish knives used succesfull? No doubt. (and kbar/bowie or puuko are "short" as fighting knives go)
Would people have used other knives given the choice? No doubt either.
But here it was about you mind your own buiseness and someone jumps you and stabs or whatever, how to defend if you have an choice
In that very limited special condition an "slasher" is not the ideal at all.
In finnish winter wars Puuko where used a lot, but again, they are first tools, second weapons, they where what people had, finnish soldiers did not consider them a weapon, they considerd them a tool that had some use as a weapon under limited circumstances.
So i say the big elephant in the room is, if you want an FIGHTING knife, do not look at TOOL knifes.
(if you want an knife for fighting purposes)
Fighting knifes are of the dirk type, double edge and pointet, some had even no edge to speak about and where basical an spike, like an real bayonet.
Then, training. No army today trains the average joe in knife fighting, so if you want to have hope to defend yourself from an surprise attack with an knife you bloody well train hard for that, and as soon it is down to wrestling distance knives are only one of many ways to defend yourself.
So my conclusion is that you get more use out of learning the bag of dirty tricks to defend against surprise attacks than fumbling for an knife stashed somewhere on your person, be it folding or not.
(trench warfare was as much using digging tools as weapons too, and theese people had bayonets as standard issue... you can not get much more close quarter combat than that but they preferred shovels quite often)
I never claimed knifes of any shape or form where not used with succes, only that they are not what was in a long bloody history of face to face combat was considerd the best choice, and that the knifes considerd a good choice where not of the form and shape you find today as "combat" knifes.
And that why i said see it as an tool, not as a weapon (but you can use it offcourse as one, succesfully, offcourse, people did it, offcourse)
An friend of mine is an very short and slim Korean and he can do things with his fingertips that are amazing, he put an guy double his weight made out of muscle out of action in front of my eyes (of the racist sort) so, if i want to protect myself against surprise attacks very close an personal (with extremly limited time to reach for an knife) well i think there is an answer.
All i said was about this very special circumstance and regarding the use of an knife (and that knives in history where more of the toolish type and not the weapon type)
yes there are plenty of documented cases where knives or similar implements where used with success, but not because people thought they where the best tool for the job, they where what they had, here it was about what do you bring if you have the choice.
