Mr Shepherd said he chose to seek asylum in Germany for several reasons: he was stationed in Germany when he decided to desert and couldn't find a way back to the US.
Germany was also significant, he said, for the historical context of the Nuremberg trials, which established the principle "that everyone, especially a soldier, is responsible for their own actions."
When asked why he joined the military in 2004, when the issue of the war's illegality was already known, Mr Shepherd said:
"I struggled through life, twice I was homeless. I didn't have access to the materials that I did when I was in Germany(...) when you look at the media in the United States, it's completely different than what it is in Europe. It's always slanted to make everything good, so you keep the war movement going."
Mr Shepherd said it was the duty of all American citizens to stand up to put an out-of-control government back on the right path and that he didn't see himself as a traitor.