The private organization that Union General George McClellan hired to help gather military intelligence was the Union Espionage Organization.
As the Battle of Antietam approached General George B. McClellan received military intelligence on the Army of Northern Virginia from three sources. One was his cavalry general Alfred Pleasonton, also from Allan Pinkerton and Maryland civilians loyal to the Union.
Directorate of General Military Intelligence ended in 2003.
Major General George B. McClellan no longer used Allan Pinkerton as a source of military intelligence as he approached what would become the Battle of Antietam. His men had found a good source in the so-called lost order of General Lee that described Lee's battle plans. With that said, he made good use of the cavalry of General Pleasanton and received information from friendly civilians.
When Confederate General Robert E. Lee decided to raid the Northern frontier by crossing the Potomac River, he found out that President Lincoln had replaced John Pope with George B. McClellan, as the commander of the the Army of the Potomac. General McClellan relied on two sources of intelligence to track General Lee's progress north. Some came from civilian observers, however, professional information came from the commander of his cavalry brigade, Alfred Pleasonton.
General Meade remained loyal to his former commander, George B. McClellan, even after Meade was appointed the leader of the Army of the Potomac. He, like McClellan outwardly criticized the political interference the military had to deal with concerning military issues.
Overestimating enemy numbers, through faulty intelligence supplied to him by Allan Pinkerton.
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.
General
US President Abraham Lincoln summoned General George McClellan to the capital. McClellan took charge of Federal troops in Washington DC on July 26, 1861. At that time he became Lincoln's most influential military adviser. In consultation with Lincoln and General Scott, McClellan developed a general plan of operations that he envisioned to be the actions of of the Union's strategic course of action. As with any military plans, the movements of Southern forces, would alter the Union's general plans. With that said, McClellan's overall initial strategies would become the basis of Federal operations against the Confederacy.
Union General George B. McClellan had a broad range of responsibilities during the eighteen months he served during the US Civil War. Only Union generals US Grant and Henry W. Halleck matched McClellan's range of military positions. On an overall basis, McClellan's combination of roles made him unique in the fours years of the US Civil War.
Lincoln's response to General McClellan's command was that Lincoln relieved McClellan of Command.
General George B. McClellan was not happy with President Lincoln's initial Emancipation Proclamation of September 22, 1862. He learned of it on September 24, 1862. McClellan discussed possible responses to the proclamation with his closest confidants. As this was happening, officers loyal to McClellan, were said to be speaking about a possible military dictatorship. McClellan, however, was never involved in that. What he did do was to speak to his Democratic friends in New York City to determine how New Yorkers would respond if he openly opposed Lincoln's proclamation.