by Meadbeard
I think John is correct in supporting Richard, however,"since you have to declare attackers all at once, the legal attack will be "used up" by the time you can ready any particular participating character,"
I'd simply add that you have to declare all the attackers for a single target at once---when this happens as part of the normal sequence of the combat phase---then the player may declare all the attackers for a second single target, even in the same engagement, then a third, etc.
This is important for heroes like Elladan, who can refresh after declaring an attack (by spending a resource), and thus may declare a second attack against a different target, since the first declaration is complete, unless . . .
Tom makes a good point regarding Quick Strike, which does not even need to occur during the combat phase.