Really? Do explain how a (by then) week old movement order that wasn't adhered to was "Lee's entire battleplan?"
The reason why McClellan was relieved, whilst in the middle of one of the most impressive movements of the war, is largely a case of paranoia. To
quote myself:
Why Lincoln Actually Fired McClellan, According to Lincoln
When discussing why Lincoln fired McClellan, it is sometimes stated it was for military reasons, and a couple of lines of a diary entry from John Hay (25th September 1864) is quoted. If one reads the whole entry a different story emerges. What Lincoln actually believed, according to Lincoln via Hay, is that McClellan really was a traitor:
The Governor Smith in question is
John Gregory Smith, who at the time in question (1862) was not governor (which he ascended to in 1863) but rather the Speaker of the House of the Vermont legislature. As even Stephen Sears noted, Smith's information was garbled and incorrect. Lincoln did send to Smith for a written account, and Smith checked with Baldy Smith. He then sent a letter to Lincoln (30th December 1864) which confirmed the entire episode was false. I have no access to this letter, which is in the University of Vermont
library archives and has not been digitised, but if Sears, who has an interest in Smith's story being true, says the letter contradicts the story I must accept it. Hence, Lincoln was acting at the time on false information. The conspiracy was a confabulation.
That McClellan's relief was not on military grounds can be demonstrated with Lincoln telling Orville Browning after the relief that McClellan was the "superior to any other general ... at handling an army in the field." (
ref) Lincoln essentially said McClellan was the best battlefield general they had, but his movements were too slow. He told Browning what he told Hay nearly two years later; that he'd issued a peremptory order and it took McClellan two weeks to start moving, and that it took McClellan six days to cross the Potomac. Of course we know that there was no "peremptory order" issued to McClellan. Possibly Lincoln gave it to Halleck as such, but Halleck's order was simply to ask McClellan to submit a plan, as discussed above.