Fitz John Porter was a career United States Army officer and a Union general during the American Civil War. He is most known for his performance at the Second Battle of Bull Run and his subsequent court martial.

The Second Battle of Bull Run or Battle of Second Manassas was fought August 28–30, 1862, in Prince William County, Virginia, as part of the American Civil War. It was the culmination of the Northern Virginia Campaign waged by Confederate Gen. Robert E. Lee's Army of Northern Virginia against Union Maj. Gen. John Pope's Army of Virginia, and a battle of much larger scale and numbers than the First Battle of Bull Run fought on July 21, 1861, on the same ground.