Why did Robert E. Lee decline command of the U.S. Army?

On April 18, 1861, Robert E. Lee was offered command of the United States Army to suppress the rebellion of the southern states. He declined the offer because, although he opposed secession, he could not bring himself to take the field against his native state of Virginia.1

In his correspondence with General in Chief Winfield Scott, Lee explained his position, stating, "Save in the defense of my native State, I never desire again to draw my sword". Following this decision, Lee resigned his commission in the U.S. Army and subsequently accepted a leadership role with Virginia's state forces before eventually becoming a prominent Confederate general.12