Who is George B. McClellan from Gods and Generals and what is their importance?

George B. McClellan was made Commanding General of the Army of the Potomac after their disastrous defeat at Bull Run. He is described as an impressive administrator, who is at times overly cautious. McClellan often requests reinforcements when he already vastly outnumbered his opponents. He nearly captured Richmond until Lee was put in charge of the southern forces and proceeded to attack him four times in seven days.

McClellan was a well loved of the Union army, and even though he was relieved of command after the Seven Days Battles, Lincoln puts him back in command after Pope's defeat at Second Bull Run.