I assume you're talking about George B McClellan from the US Civil War. He was in the Union army.
General George B. McClellan
He was very hesitant.
McClellan was a Union commander and he repelled general Lee's first Northern invasion.
Antietam
general Robert E. Lee
George B. McClellan was a general who fought in the Civil War. He fought on the side of the Union Army, but is generally regarded as a somewhat ineffective military leader.
Lincoln's response to General McClellan's command was that Lincoln relieved McClellan of Command.
Lincoln fired several generals. He fired McClellan twice.
General George B. McClellan
McClellan's Peninsular campaign failed because the Confederate army was defending Richmond better that McClellan anticipated. They retreated, then turned and attacked McClellan, surprising the Union general.
Two corps of the Army of the Potomac were under General McClellan's control at Alexandria. They were General Sumner's Second Corps and General Franklin's Sixth Corps. This totaled 25,000 troops. McClellan saw General Pope as incompetent and did not want to waste good troops to save Pope's hopeless situation. General in Chief Henry W. Halleck ordered McClellan to send these troops to reinforce Pope. McClellan held back these troops as long as possible. McClellan also urged General Pope to not engage the Rebel troops and to retreat to the north.
McClellan was a Union general (the North) and thus fought against the Confederacy (the South). He also ran against Lincoln in 1865, but lost in a severe landslide.
Unlike General George B. McClellan's frequent communications to Washington DC during the Peninsula campaign, McClellan was relatively silent concerning his plans for fighting the Confederates in Maryland and the Battle of Antietam. His immediate superior officer, General in Chief Henry W. Halleck was no notified of McClellan's intentions. It appears that all of his orders to his generals were mostly verbal and records of his side of the encounter at Antietam were sparse.
Ambrose Burnside
General George B. McClellan.
General McClellan :D
General George B. McClellan supported the Union. He was also a Democrat and supported that party which made him their candidate for the presidency in 1864.