You break their center of gravity and the knife will more likely stab them really deep rather than stabbing them directly and they pull away by reflex.
getting a hand on someone and pulling them closer to you so that they can't jump away and then strike while you are in a vulnerable slash/stab postion. control the enemies movement.
only thing i could think of when this doesn't apply is if they are trying the same thing.
Another idea is this: If you go for a stab and miss, your arm is out and the other guy can grab it and do stuff to you. By grappling him into your knife, you avoid that.
It could also help to keep it more inconspicuous. "Knife fights" generally aren't a thing. If you're trying to kill somebody with a knife, you want to do it quickly, and without anybody noticing. If you get really close to them, the knife is harder for your target and for bystanders to see. Not totally sure, though, as I don't have any actual experience. Just thought I'd take a stab at it.
That knife was the signature weapon of the Royal Marines Commando, I'd guess that this old soldier was RMC during the Second World War or maybe Korea given his age.
Fresh fruit not good enough for you eh? Well I'll tell you something my lad. When you're walking home tonight and some homicidal maniac comes after you with a bunch of loganberries, don't come crying to me!
That guy reminds me of my grandpa. Tough, wears a togue, difference is I never saw my grandpa fight. But I know he's a tough bastard cause he's 80 years old and still gets up at 5 to go to work at the paddle shop. He works for at least 5 hours a day, for no pay, just to help his son do the work he can't do alone, all while losing the feeling is his legs from age.
breaking someone's arm and then kicking them out for doubting it seems a bit harsh, especially when you just proved him wrong and he's not doubting you anymore.
You're in the military, not just the grunts, but the special forces. You are either the best, or you can get out. You will use what they teach you, or you can get out. You don't doubt what they teach you, doubt is weakness, weakness gets people killed and fails missions.
breaking someone's arm and kicking them out over a minor disagreement on knife technique seems really unreasonable, especially when you easily just proved him wrong as you were breaking his arm.
Unreasonable? It might seem that way to you and me. But given what my grandpa told about his time in the military, back in the days of the Korean War, that's not even bad.
Ever heard that you will succeed or fail as a unit?
This guy showed that he didn't believe in what he was being taught, and given that the guy who broke his arm knew how to deal with it already, we can assume they had been there for some time, meaning there was probably other lessons. How do we know he wouldn't doubt other lessons he was taught? When you're a commando, you've got to be perfect, compromise is not an option.
So now this guy has a broken arm, he can no longer train, so they give him the boot, go back to the regular army, you're not fit for us.
He was also showing that he might've been willing to attempt flawed tactics in the field, what would've happened should he have tried that maneuver on an enemy rather than a friend? Death, capture, torture, and revealed secrets. Plus tons of training and resources put to waste, plus cover blown for other units in the area.
Long story short, he might've been able to salvage his time as a commando by responding that he had been shown that he was wrong. Rather than saying that it was true that he didn't believe in the training.
he was among a group of vets we were showing around our army college in harrogate (UK training facility for junior entry to the army) while i was in training there. i remember talking to him because my grandad was a royal marine and i was telling him the stuff my grandad told me about what he got up to during his time as a royal marine, and he was telling me stuff aswell.