In the old skool, it’d be call initiative. No idea how to handle this soon-to-be-no-longer-hypothetical hypothetical case.
Character A has a strong and abiding desire to bonk Character B on the head and take him away for interrogation.
Character B is a very, very persuasive dude. So persuasive, in fact, that Character A has already run afoul of his silver tongue.
Character A wants to take Character B (probably via ICHASHITF) before Character B has a chance to open his mouth.
Hypothetical case #2 is just like #1 except the roles are reversed: mr. persuasive wants to accost the tough guy and get him talking before the tough guy can grease him.
Do we determine who gets to do what first based on whose scene it is? Because I can see this devolving into a yelling match down the road.
Also, bear in mind that “I hit him” does NOT mean “He can’t talk at me.”
The player being attacked is more than welcome to talk. This rewards player politicking over gifted roleplay or high skills: The player with Persuasion 8 can’t save his ass with it, this time. The player with Persuasion 3 and a hostage or a really good angle can. If you have the right lever, you can get the guy with the knife to turn this into a DoW himself.
It’s also legit to color your CC actions in such a way as to get more talking. The thing you can’t do is demand a DoW, or roll dice for your words. But the words can still come.
Case 2 is even more clear-cut. You need a threat or a promise for tough guy. Accost him in front of militia headquarters, say. Or offer him a lot of money. Or something else that makes him not want to kill you.
If the players are willing to work together, why test at all? In BE, spend an Interstitial scene and have the two work out their differences (the hard way if needed), so long as good story is created and both players are satisfied with the outcome (if not necessaily happy, at least accepting the agreement).
Otherwise it sounds like a simple ICHASHITF Versus test to me; test Close-Combat versus Persuasion. He who wins gets their way. After the roll, narrate the outcome. Give kudos to the Persuasion guy -if he wins- if he lets the CC guy get in a good whack before convincing him to stop.