Abner Doubleday (June 26, 1819 - January 26, 1893) was a career United States Army officer and Union general in the American Civil War. He fired the first shot in defense of Fort Sumter, the opening battle of the war, and had a pivotal role in the early fighting at the Battle of Gettysburg. Gettysburg was his finest hour, but his relief by Maj. Gen. George G. Meade caused lasting enmity between the two men.

At the start of the Battle of Gettysburg, July 1, 1863, Doubleday's division was the second infantry division on the field to reinforce the cavalry division of Brigadier General John Buford. When his corps commander, Major General John F. Reynolds, was killed very early in the fighting, Doubleday found himself in command of the corps at 10:50 am. His men fought well in the morning, putting up a stout resistance, but as overwhelming Confederate forces massed against them, their line eventually broke and they retreated back through the town of Gettysburg to the relative safety of Cemetery Hill south of town. It was Doubleday's finest performance during the war, five hours leading 9,500 men against ten Confederate brigades that numbered more than 16,000. Seven of those brigades sustained casualties that ranged from 35 to 50 percent, indicating the ferocity of the Union defense. On Cemetery Hill, however, the I Corps could muster only a third of its men as effective for duty, and the corps was essentially destroyed as a combat force for the rest of the battle; it would be decommissioned in March 1864, its surviving units consolidated into other corps. On July 2, 1863, Army of the Potomac commander Maj. Gen. George G. Meade replaced Doubleday with Major General John Newton, a more junior officer from another corps. The ostensible reason was a false report by XI Corps commander Major General Oliver O. Howard that Doubleday's corps broke first, causing the entire Union line to collapse, but Meade also had a long history of disdain for Doubleday's combat effectiveness, dating back to South Mountain. Doubleday was humiliated by this snub and held a lasting grudge against Meade, but he returned to division command and fought well for the remainder of the battle. He was wounded in the neck on the second day of Gettysburg and received a brevet promotion to colonel in the regular army for his service. He formally requested reinstatement as I Corps commander, but Meade refused, and Doubleday left Gettysburg on July 7 for Washington. Doubleday's indecision as a commander in the war resulted in his uncomplimentary nickname "Forty-Eight Hours."

what were some of his victories in the battle?
leading 9,500 men against ten Confederate brigades