James M. Mason and John Slidell, the Confederate diplomats seized in the "Trent" affair, were among those held at the fort. Confederate military officers held at Fort Warren included Richard S. Ewell, Isaac R. Trimble, John Gregg, Adam "Stovepipe" Johnson, Simon Bolivar Buckner, Sr., and Lloyd Tilghman. High-ranking civilians held at Fort Warren include Confederate Vice President Alexander H. Stephens and Confederate Postmaster General John Henninger Reagan. The prison camp had a reputation for humane treatment of its detainees. When the camp commander's son, Lieutenant Justin E. Dimick, left Fort Warren for active duty in the field with the Second U.S. Artillery, he was given a letter from Confederate officers in the camp urging good care should he be captured. (He was later mortally wounded at Chancellorsville in May, 1863.)