Clemens said Confederate Gen. Robert E. Lee had come into Maryland "for a purpose - to continue to put pressure on Lincoln and the government and to erode Northern morale."
Lee's grand strategy was to move his army into the great valley between Hagerstown and Chambersburg, Pa., where he hoped to lure a Union force from Washingon, D.C., to pursue him. Lee would then turn on his pursuers and defeat them, Clemens said, further demoralizing the North.
"Now the Union Army under (Gen. George) McClellan is under huge pressure and the troops are demoralized, disorganized and disillusioned," Clemens said.
"On the march, he molds them into an army and denies Lee every objective Lee had come into Maryland to accomplish," Clemens said.
This view of McClellan as the forceful commander is at odds with some other historians' writings, in which McClellan is painted as an indecisive, overly cautious leader who let the Confederates slip away instead of delivering the crushing blow that might have ended the war years sooner.
Clemens said he's aware of those views, but said that much of the dissatisfaction with McClellan stems from things that happened after the war, including the presidential campaign of 1864, in which the commander Lincoln had relieved ran against him for president.
To give McClellan any credit, Clemens said, would detract from Lee and Lincoln as "icons of the Civfil War."
But in fact, it was McClellan's ability to advance more quickly than expected that caught Lee's army at Sharpburg, because there was really nothing of strategic importance there.
"Lee had been distracted by the campaign for Harper's Ferry, which he had to secure to keep his supply lines to Virginia open," Clemens said.
Antietam, Clemens said, was "the first real defeat for Robert E. Lee's Army. Up until then, many people in the North were discouraged and thought that maybe it would just be better to let these people go. The whole Maryland campaign showed that there was hope."
It also remains America's bloodiest day of combat, Clemens said, with roughly 3,600 killed and 17,000 to 18,000 injured.
"At that time, Washington County only had 30,000 people. Imagine that you go the Red Cross and say you're preparing for a disaster in which a force equal to half the county's population will be severely injured," Clemens said.
It had a huge impact of the county, Clemens said, because soldiers bankrupted farmers by eating all their crops and livestock and burning fence rails for cook fires. And afterward, the rotting corpses of sodiers and animals contaminated the water, causing epidemics of typhoid.
Asked if this weekend's events will really help people understand what went on back in September 1862, Clemens said they will.
"It's very common for armchair historians to do some Monday-morning quarterbacking about what should have happened. But at an event like this, you recognize that moving 4,000 or 5,000 people from point A to point B is not so easy," Clemsn said.
"You also get an appreciation of 19th century warfare and how personal it was. More often than not, you saw, at very close distances, people who you were trying to kill and who were trying to kill you," he said.
"I don't like to get into the idea that wars are entertainment. They're not, but this event is instructive because it not only teaches and informs, but reminds us of the sacrifices made on our behalf," he said.
Directions to the events will be printed many times in The Herald-Mail this week, but if you go, Clemens suggests you take a portable radio capable of receiving AM signals, with an earpiece.
On Friday, Saturday and Sunday, he and historian Dennis Frye will narrate the action on this schedule on WJEJ AM 1240: At 4 p.m. Friday, the Battle of South Mountain; at 6 a.m. Saturday, the Battle of the Cornfield; at 4 p.m. Saturday, the Battle of Bloody Lane and on 4 p.m. Sunday, Burnside's Advance.
The McPherson book mentioned earlier is "Crossroads of Freedom: The Battle That Changed The Course of the Civil War." It's available at the Antietam Battlefield Visitors Center book store for $25.95.
And finally, for more about the Civil War history, visit www.antietam.com.
Bob Maginnis is editorial page editor of The Herald-Mail newspapers.