Lats adduct, extend, and internally rotate the arm at the shoulder. The muscles of the upper back are responsible for external rotation of the arm at the shoulder and elevation, depression, retraction, and protraction of the scapula's.
Heavy vertical/horizaontal pulling=mostly lats with a synergystic (anagonistic in some cases) muscle action from the upper back.
Face Pulls, Seated DB Power Cleans, Shrugs, Ext. Rotation work= Upper back