After the start of the Civil War, Semmes was appointed
colonel of the 2nd Georgia Infantry. He was promoted to
brigadier general on March 11, 1862. During the
Peninsula Campaign, he was a brigade commander in Brig. Gen.
John B. Magruder's Corps in the defense of
Richmond. Rushed northward at the start of the
Maryland Campaign, Semmes's brigade rejoined the
Army of Northern Virginia in the division of
Maj. Gen. Lafayette McLaws just as it was entering Maryland. His men participated in the holding action at Crampton's Gap during the
Battle of South Mountain. At
Sharpsburg, Semmes's brigade was a key part of General McLaws's strong
counterattack that stunned the
Union II Corps. In early November, his brigade was reorganized so that it only contained Georgia
regiments. Held in reserve at the
Battle of Fredericksburg, Semmes's reconstituted brigade served well at
Chancellorsville, where it blunted the advance of an entire
VI Corps division, and at
Salem Church. ==Death and legacy==