Translation:The army came into the city at night.
no, because 'entró' (entered) does not work with 'al' (to). Just like you would not say "he entered to the hotel." He entered the hotel, or he came in to the hotel.
I translated it as "The army entered into the city at night" and it said it was wrong. Can't "entrar" be translated as to enter? Is this a specific phrase, idiom, etc. for which "entered" is not correct?