The officer corps on both sides of the Civil War was a small, close-knit fraternity before the war. When General George McClellan launched his “Peninsula Campaign” intending to capture Richmond and end the war in the spring of 1862, he was opposed by the following on the Confederate side:
[Robert E.] Lee had commanded young Lieutenant McClellan in the Corps of Engineers during the Mexican War, and Longstreet too had made his acquaintance in the old army. Joe Johnston had been McClellan’s close friend in the decade before the war, and G. W. Smith his closest friend. As a junior officer, McClellan was the protégé of then secretary of war Jefferson Davis.
From Stephen Sears’s To the Gates of Richmond: The Peninsula Campaign. 
