पक्षाव् उरस्यं प्रतिग्रह इत्यौशनसो व्यूहविभागः ॥ कZ_१०.६.०१ ॥
pakṣāv urasyaṃ pratigraha ity auśanaso vyūhavibhāgaḥ
According to Auśanasa, the division of a battle array is: the two wings (pakṣa), the chest/centre (urasya), and the reserve/receiving line (pratigraha).
A three-part architecture: flanks for maneuver, a central mass for holding/penetration, and a reserve for reinforcement and recovery.