 At West Point , he was an energetic and ambitious cadet , deeply interested in the teachings of Dennis Hart Mahan and the theoretical strategic principles of Antoine @-@ Henri Jomini . His closest friends were aristocratic Southerners such as James Stuart , Dabney Maury , Cadmus Wilcox , and A. P. Hill . These associations gave McClellan what he considered to be an appreciation of the Southern mind and an understanding of the political and military implications of the sectional differences in the United States that led to the Civil War . He graduated in 1846 , second in his class of 59 cadets , losing the top position to Charles Seaforth Stewart only because of poor drawing skills . He was commissioned a brevet second lieutenant in the U.S. Army Corps of Engineers . 
