Richard Helms later became Director of the CIA. His letter to Dennis now resides in their museum.
Transcript follows. Image courtesy of The Washington Post.

Image: The Washington Post
Transcript
OBERSALZBERG, DEN V-E day
ADOLF HITLER
Dear Dennis,
The man who might have written on this card once controlled Europe — three short years ago when you were born. Today he is dead, his memory despised, his country in ruins. He had a thirst for power, a low opinion of man as an individual, and a fear of intellectual honesty. He was a force for evil in the world. His passing, his defeat — a boon to mankind. But thousands died that it might be so. The price for ridding society of bad is always high.
Love, Daddy