Translation:My brother will have returned from the war.
I'm having to think more over these expressions. Sometimes I can't decide if the sentence is past, present or future tense. Takes a bit of getting used to.
You can usually see it by the way the verb is written. For example vendt here comes from "at vende". vender - vendte - vendt. And as the word is in the past participle (the third word in the list) , that means it cannot be simply past. Then you see there is a vil in the sentence, but you already know the sentence cannot be present because the verb is in past participle. So vil cannot mean want in this sentence, so it can only mean will. So knowing you have a verb in past participle and vil as will means that you have some sort of future tense. Then you have the word være which means to have. So knowing you have will, have and a verb in past participle makes you know that it must be Future Perfect. Hope this helps!
Yes, thank you for your detailed explanation. I'll have to exercise a little more patience with these expressions though.
Why does the sentence say være before vendt, when the translation has "Have" and not "be"?
In many languages, including Danish, some verbs take "to be", rather than "to have" in the past - "at vende" must be one of them.
Sadly the English sentences we are served here are often if not entirely wrong then not very commonly used.
Like rhhpk pointed out there are words where the past tense is formed with "to be". These words mostly have to do with movement in some sense. This was pointed out in the Tips and Tricks section of "Present Perfect" under "Using »er«". It's the same in German.