Why does Gary Gallagher argue that the 1862 Richmond Campaign changed the course of the war?

Gary Gallagher argues that the 1862 Richmond Campaign significantly altered the course of the Civil War by demonstrating the effectiveness of Confederate military leadership and tactics. The campaign showcased the ability of General Robert E. Lee to inspire and lead his troops, resulting in critical victories that boosted Southern morale and confidence. Additionally, the campaign shifted the strategic initiative to the Confederacy, forcing Union forces to adopt a more defensive posture and altering their military strategies for the remainder of the war. Overall, Gallagher sees this campaign as a pivotal moment that reinforced the South's resolve and prolonged the conflict.