Book excerpt: In June of 1815 Napoleon led French forces on an offensive campaign into Belgium against the Allied Anglo-Dutch and Prussian armies under Wellington and Blucher. During this campaign Napoleon and several of his marshals made serious errors that led to missed opportunities for victory and ultimately to defeat at Waterloo. Less than 50 years later Robert E. Lee led Confederate forces on an offensive campaign into Maryland and Pennsylvania against the Union Army under Hooker initially, then Meade. A meeting engagement near Gettysburg, Pennsylvania led to three days of fighting during which Lee and several of his generals made critical errors that allowed opportunities for victory to pass and ultimately led to decisive defeat. These campaigns were remarkably alike in a number of ways. This paper reviews the campaigns and discusses similarities in the strategic settings, campaign objectives, size and disposition of forces, battlefield terrain, tactics employed, and leadership of each army. In particular, the paper compares the performances of selected French and Confederate leaders and how they contributed to the defeat of their respective armies. These comparisons provide valuable lessons learned for the conduct of future military operations.