Longstreet made his greatest contributions serving under Lee, who called him "my Old War Horse" and "the Staff of my right hand." Contrary to myth, Longstreet, not Stonewall Jackson, was Lee's intimate confidant, close friend, and principal military adviser. Contemporaries described their relationship as one of brotherly affection. Their disagreement over military affairs--with Lee stressing the Virginia theater and the tactical offensive--caused friction, but it did not lessen their mutual regard. While Longstreet was dismayed by Lee's costly attacks at Gettysburg, preferring a tactical defensive, he was neither stubborn nor disobedient during the campaign. On the second day of the battle, Longstreet's poor reconnaissance delayed his attack, but by no more than an hour, and his overall movements were not slow. On the final day of the battle, Longstreet did take longer than necessary to implement Lee's orders for an assault on the Federal center, but this was not the reason "Pickett's Charge" failed. As the attack was both flawed in concept and doomed from the start, Longstreet's reluctance was both understandable and sensible.
William Garrett Piston, "Longstreet, James," American National Biography Online, February 2000, http://www.anb.org/articles/04/04-01178.html.