Sage military commanders are made, not born. How are they made? Training, education, and experience all play a role. In other words, it is the environment, rather than the genes, that shapes great military leaders. Generalship is a complex skill and multiple factors influence its development.

Some great generals—such as Alexander the Great—enjoyed brilliant success from the beginning of their military careers. Others—such as Ulysses S. Grant—did not show unusual ability as young men. Alexander was perhaps the greatest in history. His battlefield instinct and personal courage were phenomenal, and he was very young at the time of his great conquests. Grant started slowly. For instance, he was surprised at Shiloh in 1862 and narrowly averted defeat. But he learned from it, and he did not repeat his mistakes. In the end, it was Grant who saved the Union from defeat during the Civil War.

The careers of generals are often unpredictable. Consider the case of William Westmoreland, the commander of the US Army during the Vietnam War. He had an excellent record at West Point, in World War II, and in the Korean War. At 42, he became the youngest major general in the history of the US Army. However, he tried to win the Vietnam War through attrition. His failure caused the US to ultimately lose its first war.