Complex sentence: However Davis contrasted this with the motivations for individual men in the Confederate army, writing that The widespread northern myth that the Confederates went to the battlefield to perpetuate slavery is just that, a myth.
Split into simpler sentences: However Davis contrasted this with the motivations for individual men in the Confederate army. He wrote, The widespread northern myth that the Confederates went to the battlefield to perpetuate slavery is just that, a myth.