The second deadliest battle of the American Civil War, Chickamauga is nowhere near as well-known as other battles such as Gettysburg, Antietam, or Vicksburg.  The first two were fought by the Army of the Potomac, the main Federal army fighting in the eastern theater of the war centered on Virginia.  If this army had been destroyed, the Federal cause would have been defeated.  Neither Gettysburg nor Antietam were large-scale Federal victories.  They both were emphatic ending notes to the two invasions of the Northern States in 1862 and 1863 by General Robert E. Lee and his Confederate Army of Northern Virginia.  Vicksburg meant the Confederate States were split into two as Federal control over the Mississippi came into being.