Most historians agree that the United States army could (and some have said “should”) have won a decisive victory at the Battle of Antietam and devastated the rebel army. Several times during the day Robert E. Lee made and won desperate gambles to save his beleaguered army. His opposite number, George McClellan, fixated on the chimera of over 100,000 troops facing him, failed to take advantage of several opportunities to win that overwhelming victory. The war went on, and tens of thousands more died.
My book, “Lincoln, Antietam and a Northern Lost Cause” discusses one of those opportunities, a “What If” scenario. It is available at: https://www.amazon.com/-/e/B00HV4SSWK