What is the theme in Copenhagen by Michael Frayn?

Another underlying theme of this play is that of friendship, or more specifically, how the social and political circumstances surrounding two people can strain their relationship. No one will ever know for sure how politics interfered with the relationship between the real Heisenberg and Bohr, but Frayn attempts to demonstrate that, even in times of war, fragments of friendship remained intact between the two men, at least on a fictional basis. Despite their contradictory political beliefs, their oppositional positions on either side of a brutal war, and possibly a conflict in their concepts of how scientists should use new discoveries to create destructive weapons, readers come away from Frayn's play with a sense that the deep-seated friendship between Heisenberg and Bohr was not completely eradicated.