He didn't research Lee's letters or the letters and diaries of others. He depended on secondary sources.
Let us not discount the influence two years under Fox Conner had on Dwight D. Eisenhower. He referred to this as his most profound period of military education. Fox Conner introduced him to the principles of precise and methodical military staff work and started Eisenhower on an intense military history reading program, instructing him to discuss each book and its lessons for modern warfare in detail.
Among other things, Conner made Eisenhower read about the American Civil War and Carl von Clausewitz’s,
On War repeatedly. He sought to expand Eisenhower’s intellectual horizons by introducing him to the works of Plato, Tacitus, Nietzsche, and Shakespeare—who frequently portrayed soldiers in his plays. “In describing these soldiers, their actions, and giving them speech,” Conner told Eisenhower, “Shakespeare undoubtedly was describing soldiers he knew at first hand, identifying them, making them part of his own characters.”
Drawing on his own experiences with coalition warfare during the Great War, Conner impressed upon Eisenhower three important war-fighting lessons:
1. Never fight unless you have to.
2. Never fight alone.
3. Never fight for long.
Fox Conner died on October 13, 1951, a little more than a year before Eisenhower was elected president of the United States. While he never wore more than two stars on his shoulders, three of his understudies accounted for a cumulative total of 14 stars.
Source:
September/October 2016 issue of World War II magazine.