Complex sentence: By 1863 Confederate fortunes in the region had sunk low, however, a Union campaign launched from Kansas led by General Blunt having driven the Confederacy from the north of the region, and the Cherokee having switched sides to support the Union.
Split into simpler sentences: By 1863 Confederate fortunes in the region had sunk low, however. A Union campaign launched from Kansas led by General Blunt having driven the Confederacy from the north of the region, many of the Cherokee switched sides to support the Union.