Porter reluctantly complied. As his Corps turned to head towards Jackson's right and attacked, it presented its own (and consequently the entire army's) flank to Longstreet's waiting men. About 30,000 Confederates now assailed Porter's 5,000 or so men and drove through them and into the rest of Pope's forces, doing exactly what Porter most feared would come of these orders. Pope was infuriated by the defeat, accused Porter of insubordination, and relieved him of his command on September 5.
On November 25, 1862, Porter was arrested and court-martialed for his actions at Second Bull RunPorter's association with the disgraced General George McClellan and his open criticism of Pope were significant reasons for his conviction at court-martial. Porter was found guilty on January 10, 1863, of disobedience and misconduct, and he was dismissed from the Army on January 21, 1863. It would take him nearly three more decades to clear his name.
Before Porter was court-martialed, he commanded a corps at the Battle of Antietam, where his corps became famous for its inaction. McClellan held Porter in reserve, unaware that he vastly outnumbered Lee’s split up Army of Northern Virginia, and Porter’s Corps could have made a critical difference had it been deployed that day. Porter wrote an official account of the Maryland Campaign, and it was preserved in The War of the Rebellion: Official Records of the Union and Confederate Armies. This edition of his account includes illustrations and maps of the campaign, as well as pictures of the important commanders of the battle.