When a character uses the Attack action to throw a net, he can only make one attack, regardless of the number of attacks he normally has (ex: 2 from the Level 5 Fighter's Extra Attack).
A Battle Master fighter's Commander's Strike maneuver (PHB, p. 74) enables a character to give up a bonus action and one of his attacks, when he makes the Attack action, to let an ally attack with their reaction.
Can a Battle Master with Extra Attack use the Commander's Strike maneuver after he throws a net (in order to let an ally benefit from the extra attack he cannot use by himself)?
From what I'm seeing, the Fighter character is not making more than one attack, so he's respecting the net rule, but at the same time, he does have an extra attack, which he is giving to an ally with a Commander's Strike. It all seems to work out (just like if the maneuver was tailored for net throwing!), unless I'm missing something here.
Best Answer
No. You cannot forgo attacks you can't take
You can take only 1 attack
Say your character can normally make 2 attacks by using the extra attack feature:
The net's description says:
When you attack with a net you now can take only one attack regardless of your extra attack feature.
Thus you "have" only one attack now. It is worth noting that "number of attacks you have" is not something the game ever says. The only thing that is defined is the number of attacks you can take. And that number is now 1.
You are willingly foregoing those extra attacks as a cost of using the net.
You cannot forgo attacks you can't take
Notice the word "forgo" which means "omit or decline to take". You cannot "decline to take" something that you could not have taken anyways. Like you cannot decline an invitation that was not given to you in the first place.
Since you've already used the net, you have no available attacks left to you. Thus, you have no attacks you can forgo.
Seeing as the Commander's Strike feature needs you to give up an attack and you have no more attacks to give up after using the net, then you cannot use commander's strike after using a net.
A heavy crossbow would work
Let me try to make this a bit clearer or more convincing using an example that does work.
Heavy crossbows have the loading property which says:
This is very similar to the wording of nets with the major difference being that the loading property says "you can fire only one piece of ammunition". This means that you could easily drop the weapon and continue attacking with another one given the appropriate number of additional attacks. And thus one could also use commander's strike because you still have not spent those potential attacks.
But a net will not
However, the net does not make this statement instead just saying "you can make only one Attack". The easiest way to read this in light of the above is that the net takes so long and is so unwieldy to use that you have to use your entire attack action to wield it.
tl;dr
By using a net you are spending any additional attacks you have to attack with a net. You've essentially spent them and you cannot spend then again. The idea of Commander's Strike is that is that you give extra attacks that you could have made to someone else. But in this case you could not even make those attacks and thus do not have those attacks to give.