War's Toll

[The Milkman]

Since tapping a land for mana is an activated ability, they would need to be tapped one at a time, right? So that would mean if War's Toll was on the field, if your opponent tapped one land, this card would immediately tap the rest, leaving them with only one mana, right?

For reference:

Whenever an opponent taps a land for mana, tap all lands that player controls. If a creature an opponent controls attacks, all creatures that opponent controls attack if able.

War's Toll's oracle text.

[dorsch]

No.

When your opponent taps a land for mana, War's Toll immediately triggers. Your opponent might respond to that trigger by tapping another land for mana and repeat.
But your opponent has to use all of his lands during one step.

[The Milkman]

Ah right.

True. Forgot about that.

Thanks a bunch.

[Anusien]

If you tap lands during the activation of an ability or casting a spell (the normal way), the triggers won't even go on the stack until the thing you're playing goes on the stack.