Final answer:
McClellan's Peninsular campaign failed due to his cautious strategy, failure to use his numerical advantage, and General Lee's countermeasures. His reluctance to fully engage and take risks resulted in missed opportunities and his eventual dismissal.
Step-by-step explanation:
McClellan's 1862 Peninsular campaign failed largely because he was overly cautious, hesitated to use his superior numbers, and was outmaneuvered by Confederate General Lee. General George B. McClellan was known for his reluctance to risk his troops in battle due to his belief in the overwhelming strength of Confederate forces. His cautious strategy led to missed opportunities, such as on September 17, 1862, when despite having vastly superior numbers, he failed to decisively defeat Lee, allowing the war to continue and eventually resulting in his dismissal by President Lincoln.
McClellan's advance was slowed by Confederate defenses and poor weather conditions, which halted his progress. Furthermore, when he had the chance to press his advantage and capture Richmond, his advance along the Williamsburg Road resulted in little ground gained and loss of men. McClellan's retreat on June 29 with Confederate forces in pursuit demonstrated a determination to escape at the cost of abandoning wounded and supplies.