Mutually assured destruction

[Kromm]

That sounds like two Wait maneuvers facing off and the fighters tying in the Quick Contest for cascading Waits defined on p. 108 of Martial Arts; see in particular the paragraph directly after the "Modifiers" block. It could also be a case of tying in the Quick Contest defined under Who Draws First? on p. 103 of Martial Arts; see in particular the second bullet point. In either case, the essential effect is that the two are standing off and suddenly act, and could conceivably attack truly simultaneously, with the result that neither can parry with the weapon being used to attack.

[Ulzgoroth]

Originally Posted by Kromm

That sounds like two Wait maneuvers facing off and the fighters tying in the Quick Contest for cascading Waits defined on p. 108 of Martial Arts; see in particular the paragraph directly after the "Modifiers" block.

Wouldn't that require some outside trigger, though?

[Kromm]

Originally Posted by Ulzgoroth

Wouldn't that require some outside trigger, though?

No. The rules are quite clear on this. See the second bullet point. A dialog like this is 100% rules-legal:

Player 1: "I take Wait, and will respond if he tries to attack me."
Player 2: "I take Wait, and will attack if he keeps waiting."
Player 1: "I take Wait, and will respond if he—"
Player 2: "Arrrrgh! I attack!"
GM: "Okay, you both have Wait as your last maneuver. Roll a Quick Contest."

[jacobmuller]

Originally Posted by thulben

So I'm learning a new form for my martial arts training and the last meaningful step in the form comes after the two fighters involved have disengaged and see an opening in the other guy and so go for a slash with a knife. As that's happening, both realize that to follow through with their own cut would mean that they'd get cut as well, and so both bail. My question is: are either/both of these actions resolvable in GURPS? It seems that because of the granularity of turns that it's not, but I'd be interested in being proven incorrect.

Despite the expert answers given above: no.
Defensive Attack/ Cascading Wait/ Who Draws First does resolve the combatants mutual destruction but not their decision to not attack.

I think that'd come under Common Sense (Active) and the GM tells you "If you go ahead with this attack, you're practically guaranteed to get pawned."