Textbook
Paul S. Boyer, et al., eds., The Enduring Vision: A History of the American People, 6th ed. (Boston: Houghton Mifflin Company, 2008), 435.
Lee's next stroke was even bolder. Crossing the Potomac River in early September 1862, he invaded western Maryland, where the forthcoming harvest could provide him with desperately needed supplies. By seizing western Maryland, moreover, Lee could threaten Washington, indirectly relieve pressure on Richmond, improve the prospect of peace candidates in the North's upcoming fall elections, and possibly induce Britain and France to recognize the Confederacy as an independent nation. But McClellan met Lee at the Battle of Antietam (or Sharpsburg) on September 17. Although a tactical draw, Antietam proved a strategic victory for the North, for Lee subsequently called off his invasion and retreated south of the Potomac.