Commander's Strike and meaning of 'forgo'

Question

In tonight's session my fighter just leveled to 3rd and declared as a Battlemaster; he selected Commander's Strike as one of his combat superiority maneuvers:

When you take the Attack action on your turn, you can forgo one of your attacks and use a bonus action to direct one of your companions to strike. When you do so, choose a friendly creature who can see or hear you and expend one superiority die. That creature can immediately use its reaction to make one weapon attack, adding the superiority die to the attack's damage roll.

He is a Dex-based ranged support fighter with Archery fighting style, so most of the time he will be forgoing his single crossbow shot in order to give the rogue a chance at a second sneak attack per round.

However, when he needs to enter melee, he does so with shortsword and dagger, and thus even at 3rd level he can get two attacks per turn, with the shortsword as his Attack action attack and the dagger as a bonus action attack with Two Weapon Fighting.

He would like to be able to take the Attack action with his shortsword to make his own attack, and then use Commander's Strike to forgo his dagger attack and allow the Rogue to make an attack.

However, it is not clear to me what "forgo" means, and how it interacts with the (bonus) action economy, since he might need to spend a bonus action to get the dagger attack, and also spend a bonus action to initiate the Commander's Strike. With a limit of one bonus action per round, perhaps this is not possible.

If "forgo" means 'pay for the dagger attack (with a bonus action), but don't take it', then he cannot do a Commander's Strike off of the dagger.

But if "forgo" means 'have the potential to do something but choose not to do it', then he could claim that he could use his bonus action for the dagger attack, but is instead forgoing that option to use his bonus action for Commander's Strike.

I am assuming, as this answer does, that so long as he does take the Attack action, the attack that is forgone does not have to be one generated by the Attack action, just an attack that he could have made at some point subsequent to taking the Attack action. You might disagree with those assumptions, but you need only elaborate on that if you think your answer is more persuasive or covers more ground than the competing answers to those questions already do. Instead, I would prefer that answers to this question focus on the meaning of "forgo". Ideally they would identify other uses of "forgo" in the rules that provide a clear meaning from context.

Answer 1

The attack you give up has to be part of the attack action.

The maneuver says "When you take the Attack action on your turn, you can forgo one of your attacks" -- it's talking about specifically the attacks you get from taking an Attack action, not any additional attacks you might be able to make as a bonus action, or a reaction, or whatever else. You're taking the Attack action, then forgoing one of those attacks to use Commander's Strike.

The attack you can make by using Two Weapon Fighting is not eligible to be given up for Commander's Strike because it's a separate bonus action enabled by taking an attack action, but it isn't happening when you take the attack action on your turn.

Answer 2

You cannot "forgo" an attack you cannot make

The rules for Two-Weapon Fighting state the following :

Two-Weapon Fighting: When you take the Attack action and attack with a light melee weapon that you're holding in one hand, you can use a bonus action to attack with a different light melee weapon that you're holding in the other hand.

As you've correctly noted, you need to use your bonus action to initiate the second attack. This means that if you do not have your bonus action available, you are unable to make a second attack.

The part of the rules you've quoted for Commander's Strike that are important here are the following :

When you take the Attack action on your turn, you can forgo one of your attacks and use a bonus action to direct one of your companions to strike.

While at first glance it could be a pain to determine which one of those triggers take precedence over the other, it actually does not matter, since neither of the possible orders makes it possible to use both.

If you use your bonus action to get your second melee strike through Two-Weapon Fighting, you do not have a bonus action left to initiate Commander's Strike.

If you use your bonus action to initiate Commander's Strike, you do not have a bonus action to get your second melee attack, and thus have no attack to forgo.

As such, there is no way to use both abilities at once (unless you found a way to get two bonus actions on your turn, but I've never heard of something like that).