George B. McClellan - Wikipedia

George Brinton McClellan (December 3, 1826 – October 29, 1885) was an American soldier, civil engineer, railroad executive, and politician. A graduate of West Point, McClellan served with distinction during the Mexican War (1846–1848), and later left the Army to work in railroads until the outbreak of the Civil War (1861–1865). Early in the war, McClellan was appointed to the rank of major general and played an important role in raising a well-trained and organized army, which would become the Army of the Potomac in the Eastern Theater; he served a brief period (November 1861 to March 1862) as general-in-chief of the Union Army. Although McClellan was meticulous in his planning and preparations, these very characteristics hampered his ability to challenge aggressive opponents in a fast-moving battlefield environment. He chronically overestimated the strength of enemy units and was reluctant to apply principles of mass, frequently leaving large portions of his army unengaged at decisive points.

McClellan organized and led the Union army in the Peninsula Campaign in southeastern Virginia from March through July 1862. It was the first large-scale offensive in the Eastern Theater. Making an amphibious clockwise turning movement around the Confederate Army in northern Virginia, McClellan's forces turned west to move up the Virginia Peninsula, between the James and York Rivers landing from the Chesapeake Bay, with the Confederate capital, Richmond, as their objective. Initially, McClellan was somewhat successful against the equally cautious General Joseph E. Johnston, but the military emergence of General Robert E. Lee to command the Army of Northern Virginia turned the subsequent Seven Days Battles into a partial Union defeat.

General McClellan failed to maintain the trust of President Abraham Lincoln. He did not trust his commander-in-chief and was privately derisive of him. He was removed from command in November after failing to decisively pursue Lee's Army following the tactically inconclusive but strategic Union victory at the Battle of Antietam outside Sharpsburg, Maryland, and never received another field command. McClellan went on to become the unsuccessful Democratic Party nominee in the 1864 presidential election against Lincoln's reelection. The effectiveness of his campaign was damaged when he repudiated his party's platform, which promised an end to the war and negotiations with the southern Confederacy. He served as the 24th Governor of New Jersey from 1878 to 1881, and eventually became a writer, and vigorously defended his Civil War conduct.

Most modern authorities have assessed McClellan as a poor battlefield general. Some historians view him as a highly capable commander whose reputation suffered unfairly at the hands of pro-Lincoln partisans who made him a scapegoat for the Union's military setbacks. After the war, subsequent commanding general and 18th President Ulysses S. Grant was asked for his opinion of McClellan as a general; he replied, "McClellan is to me one of the mysteries of the war."