When exactly have you "taken/used the Attack action"?

Question

There are several features with phrases similar to "When you take the Attack action" and I am wondering when exactly you have "taken the Attack action", I have found several questions and features which have ended up making this even more confusing than I originally thought.

Extra Attack says:

"You can attack twice, instead of once, whenever you take the Attack action on your turn."

This implies the following is true before getting extra attack: "you can attack once whenever you take the Attack action", which, to me, is equivalent to the following: "After you take the attack action, you can attack once" which means you would have to first take the attack action, and thus you are allowed to attack once.
And then the Fighter's Extra Attack (2) says:

"You can attack three times whenever you take the Attack action on your turn."

I can't think of a way "taking the Attack action" could mean making every available attack while having the extra attack features still work as intended.
The Battle Master Fighter's Commander's Strike Maneuver states:

"When you take the Attack action on your turn, you can forgo one of your attacks..."

If taking the Attack action meant making an entire attack then this maneuver would be useless until you acquired extra attack because you wouldn't have any attacks left that you could forgo.
Then there's the Polearm Master feat which says:

"When you take the Attack action and attack with only a glaive, halberd, quarterstaff, or spear..."

This unfortunately seems to say that "taking the Attack action" means completing all available attacks because only at that time could you know whether all your attacks were made with the required weapons.
And then there's the Way of the Four Element Monk's Fangs of the Fire Snake feature which says:

"When you use the Attack action on your turn... Your reach with your unarmed strikes increases by 10 feet for that action, as well as the rest of the turn..."

I would assume this is meant to benefit the triggering attack as well, in which case you would have to gain this benefit before you've made your first attack, which means "taking the Attack action" would happen before your first attack.
On top of all this, there's the Gloom Stalker Ranger's Dread Ambusher which has the following:

"If you take the Attack action on that turn, you can make one additional weapon attack as part of that action..." Emphasis mine

This answer here says that the additional attack must come after your first attack, due to the part that I have bolded making an exception to the general rule.
Lastly there is the Monk's Flurry of Blows feature which states:

"Immediately after you take the Attack action on your turn..."

This answer here states that you can use FoB anytime after the first attack of your Attack action. But I am not exactly sure how this works, especially with the "immediately after" bit.
And amongst all this, though his tweets are no longer official, Crawford has said the following:

"No general rule allows you to insert a bonus action between attacks in a single action. You can interrupt a multiple-attack action with a bonus action/reaction only if the trigger of the bonus action/reaction is an attack, rather than the action."

Which implies that "taking the Attack action" would actually mean making every single available attack.

All of these different features, at least to me, don't seem to have any coherent/consistent meaning of the phrase and I'm wondering if there is one supported in these books.

When have you actually taken/used the Attack action?

This matters because at what point you are considered to have taken this action determines when you can use any of the above features.

Answer 1

What if the Attack Action is during each of the Attacks?

There seems to be an implicit assumption in each of these proposals that presumes that the Attack Action has an instantaneous duration, occurring either before or after a specific Attack, and not spanning all of them.

Immediately, we know this is false: the rules are quite specific about the fact that characters are allowed to sequence other things in between their Attacks on their turn:

If you take an action that includes more than one weapon attack, you can break up your movement even further by moving between those attacks. For example, a fighter who can make two attacks with the Extra Attack feature and who has a speed of 25 feet could move 10 feet, make an attack, move 15 feet, and then attack again.

—Moving Between Attacks, Player's Handbook, pg. 190

Would this kind of rule make sense if we presumed that the Attack Action had to occur before or after one specific attack, but did not span the both of them?

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Given this understanding, let's look at each of your case studies and see how they make sense with respect to this rule:

This implies the following is true before getting extra attack: "you can attack once whenever you take the Attack action", which, to me, is equivalent to the following: "After you take the attack action, you can attack once" which means you would have to first take the attack action, and thus you are allowed to attack once.

So this is immediately incorrect. Nothing about the quoted line implies the full Attack Action must occur before any [extra] Attacks made during the turn. It simply means the Attack Action now spans multiple Attacks, which is consistent with other rules in the game.

If taking the Attack action meant making an entire attack then this maneuver would be useless until you acquired extra attack because you wouldn't have any attacks left that you could forgo.

Now that we understand that all Attacks occur during the Attack Action, it should be clear how this maneuver is perfectly workable at level 3, sans the Extra Attack feature.

This unfortunately seems to say that "taking the Attack action" means completing all available attacks because only at that time could you know whether all your attacks were made with the required weapons.

So this one is a little tricky, but the general rule is that the Bonus Action doesn't expressly say that you can interrupt the Attack Action, so we must therefore deduce that the only time this Bonus Action may be used is after the Action has fully concluded. The alternative is permitting the Bonus Action to be used at any point during the Action, provided that the character commit to never using any non-Polearm attacks at any point later in the Action, which is... a little strange, but theoretically valid.

Either way though, this is consistent with an understanding of the Attack Action occurring during all of the Attacks being made as part of it.

I would assume this is meant to benefit the triggering attack as well, in which case you would have to gain this benefit before you've made your first attack, which means "taking the Attack action" would happen before your first attack.

Yes, this does benefit the triggering attack. Interpreting the Attack Action as spanning all of the Monk's attacks in a turn is consistent with this understanding.

This answer here says that the additional attack must come after your first attack, due to the part that I have bolded making an exception to the general rule.

So to be perfectly honest, I'm not certain the Gloom Stalker feature actually requires the Ranger to only use the feature after their first attack. From where I stand, it's perfectly valid to have that extra attack occur as the first attack of the turn, because there's no requirement to have already made an Attack specified. And indeed, in that answer, you can see someone in the comments making that observation, but the answer was not edited at any point after that comment was made.

This answer here states that you can use FoB anytime after the first attack of your Attack action. But I am not exactly sure how this works, especially with the "immediately after" bit.

Immediately After is a phrase that has a lot of weight to it. it may very well mean that the Monk is not allowed to move before they use their Bonus Action, or it might mean that they are allowed to move. Regardless, one thing we know for certain is that this Bonus Action cannot be sequenced in-between the Attack(s) associated with their Attack Action.

Which implies that "taking the Attack action" would actually mean making every single available attack.

Which is how I understand it. The Attack Action spans all the Attacks made as part of that action.

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I don't think there's anything else that needs clarifying, but feel free to comment with any remaining confusion (and also make sure you add it to the original answer!) and I'll update this post to deal with those confusions as well.

Answer 2

Generally

In D&D 5e combat the combat usually goes like so;

1) Roll Initiative: Everyone involved in the combat encounter rolls Initiative, determining the order of combatants’ turns.

2) Take turns. Each participant in the battle takes a turn in Initiative order.

3) Begin the next round. When everyone involved in the combat has had a turn, the round ends.

(There are other factors to account for, such as surprised, marching speed and so on but they are not required currently)

I want to emphasise on the 2nd step.

Each participant in the battle takes a turn in Initiative order.

In a turn, you can do many things. You can move, use an object, disengage, dash, cast a spell and most usually: attack. When you tell your DM that you want to attack a target (and you haven't changed your mind) then you take the Attack action, once you have hit or missed the target with your final attack that's when your Attack action ends. Just like if you wanted to speak and nothing else, you take the Speak action and it ends as soon as you stop speaking.

In depth

"You can attack twice, instead of once, whenever you take the Attack action on your turn."

Attacking is what you do in an Attack action, just like with the Speak action you speak and nothing more. This allows the character to hit the target twice before 'spending' his Attack action. Just like you pointed out in your question: "You first take the Attack action and then attack".

"You can attack three times whenever you take the Attack action on your turn."

Same as before but now you attack three times instead of one, that means you hit the target three times.

You said: "I can't think of a way "taking the Attack action" could mean making every available attack while having the extra attack features still work as intended.".

I am really having a hard time understanding what you are asking here. Making every available attack means using your extra attack features during an Attack action.

Further into the question you ask: "If taking the Attack action meant making an entire attack then this maneuver would be useless until you acquired extra attack because you wouldn't have any attacks left that you could forgo."

No, an Attack action doesn't happen after you attack. Attacking happens after you have declared an Attack action.

"When you take the Attack action and attack with only a glaive, halberd, quarterstaff, or spear..."

That translates to "When you declare an Attack action and then attack using (...)". That means that you do not have to complete all possible attacks. Basically, if you had two attacks per Attack action you could hit the target with a glaive, drop it and then take out your dagger and hit again. (Dropping the glaive and taking out the dagger is an action on its own but supposing you could do it then it would work).

The Attack action usually happens like so:

1) Choose a target. Pick a target within your attack’s range: a creature, an object, or a location.

2) Determine modifiers. The GM determines whether the target has cover and whether you have an advantage or disadvantage against the target. In addition, Spells, Special Abilities, and other Effects can apply penalties or bonuses to your Attack roll.

3) Resolve the Attack. You make the Attack roll. On a hit, you roll damage, unless the particular Attack has rules that specify otherwise. Some attacks cause Special Effects in addition to or instead of damage.

As you can see, the last step is actually attacking the target.

"When you use the Attack action on your turn... Your reach with your unarmed strikes increases by 10 feet for that action, as well as the rest of the turn..."

What you say about the above blockquote in your question is 100% correct. When you declare an Attack action you immediately gain this feature.

"If you take the Attack action on that turn, you can make one additional weapon attack as part of that action..."

You commented saying: "I have bolded making an exception to the general rule." but there is no exception to the general rule. Again, Attack Action includes all attacks and it doesn't end before you have "spent" your last attack. It is the same as the Figther's Extra Attack "You attack twice" and "You can make one additional weapon attack" are virtually the same.

"You can interrupt a multiple-attack action with a bonus action/reaction only if the trigger of the bonus action/reaction is an attack, rather than the action."

You commented saying: "Which implies that "taking the Attack action" would actually mean making every single available attack.". No, taking the Attack action means starting an attack and having more than one. Making every single available attack means spending the Attack action.

Again the answer to When have you actually taken/used the Attack action? is:

You take the Attack action when you declare it to your DM and hit an opponent.

You have used an Attack action when your final attack ends.

Answer 3

"When you take the Attack action" means "during your Attack action".

"Immediately after you take the Attack action" means at the end of your Attack action.

This seems to be consistent with the how we'd expect these rules to work.