The version of the series run on the History Channel includes edits for some (but not all) graphic violence and profanity.
The series was actually a BBC/HBO co-production (with HBO contributing the majority of the cash). When the series aired in the UK, the title sequence began "HBO and the BBC present...". The DVD versions, and presumably all other international versions, begin "HBO presents..."
When shown on the BBC, the series was initially run with the first two episodes edited together. This meant that the opening titles were changed to account for two directors and two different writers. The Veterans' interviews for Episode 2 (Day of Days) were moved to the end of the episode before the end credits. In the programme itself, the scene with Winters sitting in the doorway gazing out at the air armada flying into Normandy is smoothly blended into the 'flying clouds' sequence that begins Episode 2 (which is much shorter).
All episodes except the third were rated "Not under 16" in Germany. For commercial reasons (films with a rating higher than "Not under 16" are restricted in distribution and may not be sold online) the third episode, which was rated "Not under 18", was edited for violence. The uncut DVD is available separately in video stores in a red snapper case.