The fight on Little Round Top was the decisive action on the second day during the Battle of Gettysburg. Little Round Top, defended by the brigade of Colonel Strong Vincent, was the extreme left flank of the Union position. It was important for two reasons: First, it had to be held in order to protect the Union left. More importantly, it served as protection for the left of Cemetery Ridge, a key position being held by Federal troops. If Little Round Top was captured by the Confederate troops, not only could the Union left be turned, but Cemetery Ridge would be exposed to artillery fire and would have to be abandoned.
Little Round Top was still undefended on the second day of battle, but both sides recognized the importance of the location. On his own initiative, Vincent marched his four regiments to the top of the hill. Crack Confederate troops under Brigadier General Evander Law (of Major General John Bell Hood's famous division) stormed the slopes, only to be repeatedly repulsed by Vincent's brigade. Vincent received what would prove to be a mortal wound, and Colonel Joshua Chamberlain took charge. When he realized his dwindling troops had little ammunition left, Chamberlain ordered two classic military maneuvers, first turning his formation to "refuse the line." Seeing the Confederates preparing for yet another charge, Chamberlain ordered a "right wheel flank"--a "simultaneous frontal assault and flanking maneuver"--advancing his left flank forward in a bayonet charge; when they were aligned with the remaining troops, the entire force--though heavily outnumbered--advanced downhill at the tired and surprised Alabamans. This maneuver was akin to the closing of a swinging door, and the Southern troops were routed, with a large number of troops captured. Chamberlain's attack by such an inferior-numbered force became one of the greatest triumphs of the war, and certainly proved to be the decisive action of the second day's action at Gettysburg. Chamberlain was later awarded the Congressional Medal of Honor for his day's work.