For conducting his operations so slowly that some of the cabinet questioned his loyalty to the cause. Lincoln said "If General McClellan does not want to use the army, perhaps I may borrow it for a while."
Inaction. Lack of command ability. In short, he didn't fight well.
because he noob
Lincoln fired several generals. He fired McClellan twice.
General George B. McClellan
George McClellan
Major General George Brinton McClellan.
General of the Union Army; fired by Lincoln for being too cautious
lincoln
Lincoln fired McClellan twice.
McClellan has that honor.
Based on his previous actions, and not just those at Antietam, Lincoln fired Major General George McClellan as general-in-chief of the Union armies and replaced him as commander of the Army of the Potomac with Ambrose Burnside.Lincoln was likely prompted by what he saw as the indecisive, overcautious nature of McClellan, who at Antietam thought that he was outnumbered when it was very much the reverse.
Lincoln fired McClellan twice.
7 famous generals were fired by Lincoln. They were: Irwin McDaniel, George B. McClellan (who was rehired and refired), John Pope, Joe Hooker, Franz Sigal (also fired twice), John C. Fremont (also fired twice), and William Rosecrans.
Eventually fired him. "If General McClellan does not wish to use the army, perhaps I may borrow it for a while."