Long before he became best known for Ben Hur, Lewis "Lew" Wallace (April 10, 1827 – February 15, 1905) was an important Union general who played significant roles in the Western theater at the outset of the war. 
Wallace was able to organize two full brigades and a third incomplete, and took up position in the center of Grant's lines besieging Fort Donelson. During the fierce Confederate assault on February 15, Wallace coolly acted on his own initiative to send a brigade to reinforce the beleaguered division of Brig. Gen. John A. McClernand, despite orders from Grant to avoid a general engagement. This action was key in stabilizing the Union defensive line. After this Confederate assault had been checked, Wallace led a counter attack which retook the ground that was lost. Wallace was promoted to major general to rank from March 21.
However, confusion during the Battle of Shiloh would cost Wallace dearly. Miscommunication between Grant and Wallace led to Wallace not bringing his division up in time to help stop the rout that was on during the first day, and Grant and Henry Halleck would later pin the blame on Wallace, although historians do not believe the miscommunication was actually his fault. At first, there was little fallout from this. Wallace was the youngest general of his rank in the army and was something of a "golden boy." Soon, however, civilians in the North began to hear the news of the horrible casualties at Shiloh, and the Army needed explanations. Both Grant and his superior, Halleck, placed the blame squarely on Wallace, saying that his incompetence in moving up the reserves had nearly cost them the battle. Sherman, for his part, remained mute on the issue. Wallace was removed from his command in June and reassigned to the much less glamorous duty commanding the defense of Cincinnati in the Department of the Ohio during Braxton Bragg's incursion into Kentucky.
After the war, Wallace wrote an account of the Battle of Fort Donelson that was published in the well known Battles & Leaders series. This edition is specially formatted with images of the important military commanders.