Translation:The Klingon Empire has conquered many star systems.
The -ta' on chargh in this sentence indicates that the action of conquering was complete and intentional. We don't really have a clear and consistent way to indicate that well in English. The sentence, "The Klingon Empire conquered many star systems," can, indeed, be used in English in the exact same circumstances and with the exact same meaning as the Klingon sentence given. However, how then do we account for the -ta' in the Klingon sentence. As this course was being created, a decision was made to have separate translations for sentences with -pu'/-ta' from those without. Thus, when you see -pu' or -ta' on a verb, in this course, you will need to put the English prefect tense (and vice-versa), even though the match is not ideal. It's not a perfect solution (pun not intended, but hopefully appreciated), but it is how this course has been designed. So, in translations outside of Duolingo, no, it is not really necessary, but in this course, yes, we will require you to use it to acknowledge the suffix.