Present perfect tense and past perfect tense
Sentence: After having been wounded towards the end of the war, he had been sent to hospital.
a) 'After having been wounded'
Can this part be replaced with 'After wounded'? If no, why not? If yes, is there any difference between the two?
b) Generally speaking, is there any difference between present perfect tense and past perfect tense in describing something happened in the past? Because there are many passages using both two describing the same story. I don't refer to the sentence above, but unfortunately at the moment, I can't find an example.