On the second day of fighting at Gettysburg, Confederate Gen. Robert E. Lee listened to scouting reports, scanned the battlefield, and ordered his second-in-command, James Longstreet, to attack the Union Army's left flank. It was a fateful decision, one that led to one of the most desperate clashes of the entire Civil War: the fight for a piece of ground called Little Round Top. The Union's defense of the boulder-strewn promontory helped send Lee to defeat at Gettysburg, and he never again ventured into Northern territory. Why did the shrewd and canny Lee choose to attack, especially in the face of the Union's superior numbers? While historians have long wrestled with that question, geographers and cartographers have come up with an explanation.
Their sophisticated mapping software shows the rolling terrain exactly as it would have appeared to Lee—and from his vantage point (he is believed to have surveyed the battlefield from a pair of cupolas), he simply couldn't see throngs of Union soldiers amid the hills and valleys. "Our analysis shows that he had a very poor understanding of how many forces he was up against, which made him bolder," said Middlebury College professor Anne Knowles, whose team produced the most faithful re-creation of the Gettysburg battlefield to date, using software called GIS, or geographic information systems. You can see the panoramic map on the Smithsonian website; click for more on their analysis. (Read more civil war stories.)