Learn Arabic (Modern Standard): كنا سنهاجم هجوما مفاجئا، لكن الطقس ساء. - We were going to attack suddenly, but the weather worsened.

To express the 'future in the past' (something you intended or were about to do), you use the past tense of كان (to be) followed by a present tense verb with the future prefix سـ or the word سوف. Here, كنا (we were) is paired with سنهاجم (we will attack) to mean 'we were going to attack'.

The English translation says 'attack suddenly', but the Arabic repeats the word for attack: سنهاجم هجوما مفاجئا. Why is this?

Arabic often uses a structure called the absolute object (Maf'ul Mutlaq) to describe how an action is done. Instead of using a direct adverb for 'suddenly', Arabic repeats the verb as a noun: literally, 'we were going to attack a sudden attack'. هجوما is the verbal noun (masdar) of the verb نهاجم.

Why do the words هجوما مفاجئا both take the accusative case (mansub) with the '-an' ending?

هجوما takes the accusative case because it acts as the absolute object of the verb. Then, مفاجئا is an adjective describing that attack. In Arabic, adjectives must perfectly match the noun they describe in case, so it also takes the accusative ending.

I don't recognize the verb ساء. Is it related to the word for 'bad'?

Yes! ساء is a past tense verb meaning 'to become bad' or 'to worsen'. It shares the same root letters as the common adjective سيء (bad).