Confederate Robert E. Lee’s Army of the Northern Virginia took its fight to Maryland 150 years ago this week in the Civil War.

Lee’s forces clashed with Union foes on Sept. 14, 1862, at the Battle of South Mountain, Md. Fighting here would be a mere prelude to the monstrous Battle of Antietam in three days’ time. Lee’s hope was to crush Northern war spirits by taking the fight to Union turf.

Lee’s troops briefly occupied Frederick, Md., but soon were chased off by the approaching Union forces of Major Gen. George B. McClellan. Because a copy of Lee’s battle plan had accidentally fallen into Union hands, McClellan had advance word that Lee would send part of his fighting force to capture Harpers Ferry, in present day West Virginia, while leaving Maryland’s South Mountain gaps lightly guarded.

In fierce fighting at South Mountain, McClellan sought to crush the Army of Northern Virginia. But it was to no avail. Lee regrouped his far-flung divisions to fight another day. Only days ahead, the two foes would meet at Antietam, a turning point in the Civil War.

Still, there was little inkling this week of the deathly battle that was near. The Associated Press reported on Sept. 13, 1862, that Union fighters who drove Confederates from Frederick after some skirmishing were cheered when they reached that Maryland city: “The entire city appeared overjoyed to see us again, and the people turned out en masse to welcome our troops … flags were waved from house-tops and windows and the side walks were thronged with people, including a full representation of ladies.”

But AP also reported in the same dispatch that there were reports of a huge Confederate force numbering more than 100,000-strong still out and about in the countryside.