indefinido and imperfecto

Question

I don't understand why the imperfect "Teníamos que llevar" is used and not the preterite. After studying again when to use imperfect, it would seem that this sentence is " We used to have to wear" or "We were having to wear", whereas "We had to wear" would be "Tuvimos que llevar".  I can't see how the phrase "We had to wear protective hats" suggests it is ongoing and not completed. Obviously I'm wrong but I don't get it.

Accepted Answer

Hola Peter
You can use both here "teníamos que llevar" and "tuvimos que llevar". It depends on what you want to convey. The Indefinido would be used if we see this as a completed action; the Imperfecto is used when we are simply describing and not seeing this as an action with an end. You're right at thinking that the Imperfecto is also used when what we mean is "used to [do something]" or "was doing [something]" but this is not exactly what we mean in this sentence; this is why we are using the translation "had to wear".  We are seeing the action of having to wear a helmet as something with no specific end.
Here's a lesson where we explain this nuance when we are not using time markers. You'll see how the translations are the same for both. Indefinido vs Imperfecto.
Having said that, we will add a hint to that writing exercise saying that you need to use the imperfect in that sentence as it is true that no other element in the sentence will give you the clue to use one or the other. I hope that helps.
Saludos cordiales
Inma