Arvid and Mildred were arrested on September 7, 1942. On December 19, Arvid Harnack was sentenced to death and executed on December 22, 1942 for his role in the Red Orchestra. Arvid Harnack was one of the leaders of the Harnack/Schulze-Boysen group which was part of the 'Die Rote Kapelle', as it was known in German. The Red Orchestra was an anti-Hitler, underground resistance organization. Spread throughout Europe, they attempted to bring an end to the war as quickly as possible and, in the case of Harnack's group, to ensure the national existence of Germany.
 
The following two retyped and reformatted letters were written by Arvid right before his death. One is addressed to his family and one to his wife of 16 years, Mildred Fish Harnack.
 
On the day of his execution, he writes his family that they "...should celebrate Christmas well. That is my last wish." and that he "would like to thank...[them] all again for all...[their] love which...[they] have shown...[him], especially of late. Thinking of it made all heaviness seem light."
 
In Arvid's last letter to Mildred, he reminds her of their beginnings - their first deeply meaningful discussion and their engagement while attending the University of Wisconsin - Madison. "Can you remember Picnic Point, when we got engaged?...And before that our first serious talk at lunch in a restaurant in State Street? That talk became my guiding star and has remained so." He ends with the following: "You are in my heart...My greatest wish is that you are happy when you think of me. I am when I think of you. Many, many kisses! I hug you tight. Your A."