Served in Corps Engineers, United States Army, Louisiana, 1838-1846. Member of staff General Scott as engineer during Mexican War, 1846-1847. Received brevets for conduct at battles of Cerro Gordo and Contreras.
Promoted captain, 1853, served in Corps Engineers. Appointed superintendent United States Military Academy, 1860, resigned to join Confederate Army, 1861. Commissioned brigadier general Confederate Army, 1861, major general, 1861.
2d in command at 1st Battle of Bull Run, 1861. In command Confederate Army at Battle of Shiloh, 1862. Retreated from Corinth (Mississippi) after fortifying it.
In charge of coastal defense of Georgia and South Carolina., 1863. Served in Virginia theater, defeated General Butler, fought at Battle of Petersburg, 1864. 2d in command to General J. E. Johnston in Carolines, circa 1865.
President New Orleans, Jackson & Mississippi R.R., circa 1866-1871. Served as adjutant general of Louisiana for many years after war. Author: Principles and Maxims of the Art of War, 1863.
A Commentary on the Campaign of Manassas, 1891.