From the Civil War in Northeast North Carolina Blog.
Alexander M. DeBree was held prisoner at Fort Warren in Boston Harbor between December 1861 and February 1862. He was one of 124 Confederate prisoners held there.
But, if you had to be in a Union prison, this was the one you wanted to be at as it had the reputation for treating its prisoners the most humanely.
Now, this is a bit surprising as he was not in Confederate service before this time. Why was he held? What had he done to be put into prison like this?
I am thinking he was probably out on a Navy warship and oversees when the war broke out. When the ship returned, most likely he refused to take the Oath of Allegiance to the United states (because of his Southern upbringing) and was summarily dismissed from U.S. navy service and imprisoned. It was not long after his release that he entered Confederate Navy service.