Breakdown of An der großen Kreuzung mussten wir rechts abbiegen.
groß
big / tall
wir
we
müssen
to have to, must
an
at, on (vertical) / to (addressee) / of (in quantity/stock expressions)
Questions & Answers about An der großen Kreuzung mussten wir rechts abbiegen.
Why does the adjective groß have an -en ending here?
This sentence uses the dative case because of the preposition an. As you are learning in this lesson, when you have a definite article (like der here) in the dative case, the adjective following it always gets an -en ending, no matter the noun's gender. So groß becomes großen.
Why does the feminine word Kreuzung use the article der?
The preposition an is a two-way preposition. Since it describes a fixed location here (where the turning happens), rather than movement towards a new destination, it triggers the dative case. In the dative case, the feminine article die changes to der. As a handy reminder, nouns ending in -ung are always feminine!
Why is it mussten wir instead of the spoken past like haben wir gemusst?
The word mussten is the simple past tense (Präteritum) of müssen (to have to). Even in casual, everyday spoken German, native speakers almost always use the simple past forms for modal verbs instead of the conversational past (Perfekt). It sounds much more natural.
The verb abbiegen (to turn) is a separable verb. Why isn't the ab- prefix separated?
Because of the modal verb mussten (had to). A modal verb always pushes the main verb to the very end of the sentence in its full, unchanged dictionary form (the infinitive). Because it is in the infinitive, the prefix stays attached to the rest of the verb.