Answer:
General McClellan’s most grievous error was hugely overestimating Confederate numbers. This delusion dominated his military character. In August 1861, taking command of the Army of the Potomac, he began entirely on his own to over-count the enemy’s forces. Later he was abetted by Allan Pinkerton, his inept intelligence chief, but even Pinkerton could not keep pace with McClellan’s imagination. On the eve of Antietam, McClellan would tell Washington he faced a gigantic Rebel army “amounting to not less than 120,000 men,” outnumbering his own army “by at least twenty-five per cent.”
Explanation:
For those who might not be familiar with the term, a Pyrrhic victory is
technically a win, but the results of the victory or the casualties
incurred in the process of achieving the victory are absolutely
devastating to the victor, either physically or emotionally, to the
point where calling the campaign a victory is arguable depending on the
observer’s perspective.Pyrrhic victories are popular in works that take place in a darker or
more cynical setting. They pop up in almost all of Shakespeare’s
tragedies (Hamlet is a great example), and a good deal of post-apocalyptic literature will feature at least one Pyrrhic victory.