Gen. George McClellan's Peninsula campaign mirrored the rise and fall of Northern morale during the spring and early summer of 1862. Northerners sensed victory in May when McClellan's force camped six miles outside Richmond, but morale collapsed in July as Lee drove a hesitant McClellan twenty miles backward to the James River in seven days. Once again claiming that he and his men were outnumbered, McClellan called for reinforcements and planned a second march to Richmond. Lincoln responded by replacing McClellan as general-in-chief of the army with Henry W. Halleck and ordered "Little Mac" back to Washington.

Militia Act.

Unlike a year earlier, when Northern resolve hardened after the first defeat at Bull Run, the Northern response wavered after Lee's counteroffensive in 1862. New recruits trickled into Union recruiting offices after the Seven Days' fiasco. Congress then passed a Militia Act in July authorizing...