GURPSよろず

Stop Hits
It has often been in vogue among swordsmen to attack an opponent as he attacks or prepares to attack, the idea being to stop his blow and hit him while he’s committed to attacking. There are many variations on this tactic, known as “attack on preparation,” “stop cut,” “stop thrust,” and “time thrust.” Such gambits aren’t limited to swordplay; Bruce Lee (pp. 24-25) was an advocate of the “intercepting fist.” For game purposes, the collective term for these moves is Stop Hit – if only to distinguish them from the “stop thrust” on p. - B366.
To try a Stop Hit, take a Wait and declare that you intend to attack your foe. Instead of simply attacking first, which allows him to parry and continue with his attack, you attack into his attack in an effort to hit him while he’s on the offensive and less able to defend. Since you’re on the offensive, too, this is a gamble: your skill against his.
You and your opponent both roll to hit normally. If you both miss, nothing happens. If one of you hits and the other doesn’t, the struck fighter defends at -1 . . . or at -3 if he tries to parry with the weapon he used to attack. If you both hit, the one with the largest margin of success defends normally while the other has the penalty above – but in a tie, you both suffer this penalty!
You can do this with an unbalanced weapon (one with a “U” in its Parry statistic) or even one that becomes unready after an attack – and if you do, you can try to parry your foe’s weapon. This is because your Stop Hit and parry are a single move, not two distinct actions. You cannot parry after your Stop Hit, however.
See Counterattack (p. 70) and Riposte (pp. 124-125) for two related ways to take advantage of an attacker.