As a young boy, MacArthur dreamed of following in the steps of his famous father, an army captain who won the Congressional Medal of Honor during the Civil War. His mother told him, "You must grow up to be a great man—like your father and Robert E. Lee." When Douglas was 13, he overheard his father say to her, "I think there is the material of a soldier in that boy." He never forgot that remark. William Manchester wrote, "No adolescent rebellion for him; all his life he would seek to be a man-at-arms in whom his father could have exulted."

Douglas excelled at sports and academics, but when he graduated high school in 1897, he was denied entry to the United States Military Academy at West Point, New York. He did not receive the presidential appointment he needed, and he also failed his preliminary physical examination due to curvature of the spine. But there was indeed material of a soldier in this young man: He moved with his mother to a district in Wisconsin where they knew the congressman and immediately set out to correct the spinal defect with the help of a specialist, whom he worked with an entire year! He was determined not to be denied West Point in 1899. The doctor said of him, "He was one of the quickest fellows to obey orders I have ever treated. He was tremendously interested in anatomy, biology, physiology and everything that concerned health and medical science."

Meanwhile, Douglas also worked with his mother as well as a tutor to prepare for a contest in his congressional district, walking two miles every day to study. He said he never worked harder in his life. The night before the contest he had trouble sleeping. His mother told him that day: "Doug, you’ll win if you don’t lose your nerve. You must believe in yourself."