Complex sentence: Again the Dark One took the offensive and gradually began to push the forces of the Light back again, as more and more of his generals defected to the other side, convinced Lews Therin Telamon and the forces of Light would lose.
Split into simpler sentences: Again the Dark One took the offensive and gradually began to push the forces of the Light back. As more and more of his generals defected to the other side, Lews Therin Telamon became convinced that the forces of Light would lose.