Complex sentence: To the misery of Cao Cao's army, the allies, led by Zhou Yu and Liu Bei, gave chase over land and water until they reached Nan Commandery (南郡); combined with famine and disease, this decimated Cao Cao's remaining forces.
Split into simpler sentences: To the misery of Cao Cao's army, the allies, led by Zhou Yu and Liu Bei, gave chase over land and water until they reached Nan Commandery (南郡). Combined with famine and disease, this decimated Cao Cao's remaining forces.