"When the brothers were reunited, Hans explained how it was that he was still alive. After having been wounded towards the end of the war, he had been sent to hospital and was separated from his unit. The hospital had been bombed and Hans had made his way back into Western Germany on foot. Meanwhile, his unit was lost and all records of him had been destroyed. Hans returned to his family home, but the house had been bombed and no one in the neighborhood knew what had become of the inhabitants. Assuming that his family had been killed during an air raid, Hans settled down in a village fifty miles away where he had remained ever since."
The narrator sets the two situations "was separated from his unit" and "his unit was lost" in simple past tense. My understanding is that it is for reasons of style, because if "had been separated" and "had been lost" were used instead, then there would be too many had-been's one after another in the text. Is my understanding correct?
If so, my second question is, how, when we are writing stories, should we make a choice as to which verbs can be switched to the simple past and which cannot for a whole passage in the past perfect ?