Translation:Ten years after the great defeat.
Since joining Duolingo, I have found this type of structure. I have asked the same question as you and I have reported it each time. I believe one should not use a period when it is an incomplete sentence. Also it could have somehow gotten into the wrong skill. Who knows! In this case, probably someone gotten confused on the noun defeat and the verb 'to defeat'.
Yeah, I'm not exactly mad at DuoLingo. (I'm in it for the owl. ^_^)
I realized "derrota" looks like a conjugated verb form, and I've been wondering if perhaps DuoLingo is programmed in a way that doesn't allow it to recognize whether or not "derrota" is a verb form or the noun. Perhaps DuoLingo has the same problem with English words like "swimming" when teaching the English courses to other speakers.
I think it's important to point out the bad grammar in both languages, especially since DuoLingo uses translation exercises as its dominant method of teaching. Even though I read that some people don't really care about the English grammar because they want to learn Spanish, there are perhaps others on here who, like me, care about not only being fluent in both languages but also being able to write equally well in both.
They're probably just teaching that certain verbs can be referred to in noun form. In English we don't bat an eye when someone refers to verbs as events, such as "the defeat" or "the hunt". I'm betting in most languages they have some parallel constructs, where verbs can take noun form without any extra work.
"despues de" and "antes de" are fixed phrases in Spanish that are used for "before" and "after"
Usually with an infinitive verb, or a noun after.
Despues de despertarme (after I wake up)
Despues de la tormenta (after the storm)
Antes de comer (before eating)
Antes del fin (before the end)
This will vary depending on the rest of the sentence. Time expressions are not necessarily direct equivalents between Spanish and contemporary English. You wouldn't use 'después de' though, if that's what you really want to know. Since and ago are most commonly expressed with 'hace'+ time frame. It depends on what the complete thought is.
You are correct. They would still attach an adjective describing sentiment over one describing size, however. "It was a //terrible// defeat for our homeland!"
edit: to be clear, yours is comprehensible just somewhat strange. It's okay to attach an adjective describing size to victory/defeat, but it's not the most common way we say things in English, in my experience. I'd say, "It was a major defeat," "It was a great defeat," or "It was a terrible defeat," depending on sentiment. The first would contain the least bias :)