Return to Answer

Q. @JeremyECrawford When you take the Attack action, is the trigger for the two-weapon fighting bonus action attack the entire Attack action or a single attack within the attack action? Can that particular bonus action interrupt the Attack action?

 

A. Here's the trigger for the two-weapon-fighting bonus action: "When you take the Attack action and attack with a light melee weapon that you're holding in one hand …." (PH, p. 195).

 

Summary: the trigger is the attack that's part of the Attack action, not the entire action. [this summary is part of Crawford's tweet]

Q. @JeremyECrawford When you take the Attack action, is the trigger for the two-weapon fighting bonus action attack the entire Attack action or a single attack within the attack action? Can that particular bonus action interrupt the Attack action?

A. Here's the trigger for the two-weapon-fighting bonus action: "When you take the Attack action and attack with a light melee weapon that you're holding in one hand …." (PH, p. 195).

Summary: the trigger is the attack that's part of the Attack action, not the entire action. [this summary is part of Crawford's tweet]

What do the rules actually say?

What we can see from looking at the rules is that there exists a section on "Moving Between Attack" which explicitly allows you to move between attacks of an action. There is no similar section allowing you to insert a bonus action between the attacks of an action. Thus, you cannot use any bonus action in-between the attacks of the Attack action regardless of its trigger, even if it has no trigger whatsoever.

This, however, is a rather odd situation and is not something I have ever seen used at the tables I've been a part of, nor is it a ruling I would use at my own tables. Even Jeremy Crawford himself disagrees with this ruling here:

A bonus action that has no trigger—such as Cunning Action and the misty step spell—can take place whenever you want on your turn (PH, 189).

How I actually run my tables

I am all for giving my players more options; if they want to break up their Attack action with Two-Weapon Fighting or some other bonus action, I will always give them that option. This is simply because I don't find it particularly helpful to have some bonus actions able to be used mid-Extra-Attack and others could not be based on small differences in wording that the rules themselves don't even cover.

Otherwise, it depends on whether the trigger for Two-Weapon Fighting is the Attack action or an attack with a light melee weapon

All of these things can be put together to conclude that, according to Crawford, things that use your bonus action or reaction which first require you to "take the Attack action" cannot be done until the Attack action itself is fully resolved. This all would mean that you can use the bonus action only after every attack of the Attack action.

So there's a lot of wiggle room for interpretation with the timing of the bonus action attack from Two-Weapon Fighting, so at the end of the day I'd say it falls to your GM. You might also think the it doesn't really matter whether you can use TWF mid-Attack-action, however:

The rules state that you can take a bonus action at any time unless its timing is specified, in which case you follow the bonus action's own restrictions

You choose when to take a bonus action during your turn, unless the bonus action’s timing is specified [...]

This explicitly details that bonus actions can be taken whenever you want on your turn, and there is no reason this would not include times such as in-between actions that involve multiple attacks.

If a bonus action has a specified timing then you must first satisfy that individual bonus action's timing requirements.

With Two-Weapon Fighting in particular, it depends on whether the trigger is the Attack action or an attack with a light melee weapon

All of these things can be put together to conclude that, according to Crawford, things that use your bonus action or reaction which first require you to "take the Attack action" cannot be done until the Attack action itself is fully resolved. This all would mean that, if Two-Weapon Fighting is triggered in part by "taking the Attack action" then you can use the bonus action only after every attack of the Attack action has been resolved.

How I actually run my tables

I am all for giving my players more options; if they want to break up their Attack action with Two-Weapon Fighting or some other bonus action, I will always give them that option. This is simply because I don't find it particularly helpful to have some bonus actions able to be used mid-Extra-Attack and others could not be based on small differences in wording that the rules themselves don't even cover.

There's a lot of wiggle room for interpretation with the timing of the bonus action attack from Two-Weapon Fighting, so at the end of the day I'd say it falls to your GM. You might also think the it doesn't really matter whether you can use TWF mid-Attack-action, however:

What we can see from looking at the rules is that there exists a section on "Moving Between Attack" which explicitly allows you to move between attacks of an action. There is no similar section allowing you to insert a bonus action between the attacks of an ation. Thus, you cannot use any bonus action in-between the attacks of the Attack action regardless of its trigger, even if it has no trigger whatsoever.

What we can see from looking at the rules is that there exists a section on "Moving Between Attack" which explicitly allows you to move between attacks of an action. There is no similar section allowing you to insert a bonus action between the attacks of an action. Thus, you cannot use any bonus action in-between the attacks of the Attack action regardless of its trigger, even if it has no trigger whatsoever.