Ulysses Grant was the United States greatest general since George Washington. Like Washington, Grant's battlefield performance in the Civil War was the only factor standing between the United States continuing as one, indivisible nation. Grant was the keystone of Union victory, a man whose removal would have resulted in the Union cause crumbling into defeat - and the United States dissolving into a collection of competing sovereign states.
It was not always so clear cut. Am early military career had ended with his resignation for alleged drunkenness, while in civilian life a number of his business ventured foundered leading to the nickname "Useless" Grant. Then the Civil War began. Because he had military experience - he had gone to West Point and served in the Regular Army as an officer - when Grant enlisted in the Army, he became a Captain in an Illinois volunteer regiment. Through sheer competence - and overcoming a bad reputation - he quickly rose to colonel, brigadier general and then major general Grant. After he led the first successful major Union offensive of the war - which resulted in the capture of Forts Henry and Donelson - "Useless" Grant disappeared, replaced by "Unconditional Surrender" Grant.