Two different "versions": In West Germany the miniseries originally was released in 1985 as a version with three 100-minute episodes. Two years later, in 1987 the series was re-broadcast but this time consisting of six 50-minute episodes (basically, the three original episodes were split into two episodes each, which results in a total of six episodes). Each episode has a short recap at the beginning and a short preview at the end.
The German 6-part version also has an alternative title for each episode:
Part 1: Operation Atlantik (Operation Atlantic) Part 2: Auf Suchkurs (On Search Course)
Part 3: Der erste Angriff (The First Attack) Part 4: Himmelfahrtskommando (Suicide Mission)
Part 5: Auf Grund (On Ground) Part 6: In der Heimat (At Home)