Ulysses S. Grant began his military service in 1839 when he entered the U.S. Military Academy. Upon graduation in 1843, he was assigned to an infantry regiment that was destined for duty in the Mexican War. Grant participated in most of the major Mexican War campaigns and after the War would continue on active duty until 1854. Ten years later, Lieutenant General Ulysses S. Grant, Commander in Chief of the Union Army, would conceive and orchestrate the Campaign that ended the Civil War. The purpose of this book is to explore Grant's development as a military leader by researching his personal correspondence. His understanding of national strategy and the operational level of war was the focus of this work. In addition, Carl Von Clausewitz's concept of "military genius" was used to analyze Grant's military intellect. The study revealed that he possessed a sharp military intellect based on common sense and that his understanding of national strategy and the operational art is worthy of study by all military professionals.