This is an awkwardly phrased statement, and I think the word order is wrong. It's not entirely clear what it means, so it's potentially ambiguous. What it seems to mean is very, very unlikely to be true: 1. "He had served for forty years in the army before." In theory, it could mean this. For example, if someone is currently serving a five-year prison sentence, you could say "He had served five years in prison before", meaning that this was the second time that he had spent a five-year stretch in prison. However, that it is practically impossible. Nobody can serve 40 years in the army at two different periods of their life! 2. I think that the writer means 'He had served in the army 40 years before'. This means that he had been in the army at a certain point in time : this was 40 years earlier than the point in the story which we are describing. If the story is set in the 1990s, for example, it means that he had served in the army at some point during the 1950s. I can see why you're confused.

2. Forty years ago, he served in the army.