The Tarkin Doctrine (the Imperial military strategy championed by Grand Moff Wilhuff Tarkin) is centered on the "Rule through Fear." It prioritizes centralized authority, massive capital investment into planet-killing superweapons (most notably the Death Star), planetary orbital bombardment, and the psychological intimidation of star systems to deter insurrection, operating on the premise that overwhelming terror will render active resistance impossible.
In contrast, the Thrawn Doctrine (advocated by Grand Admiral Thrawn) prioritizes conventional military efficiency, tactical flexibility, and asymmetrical counter-insurgency. It redirects imperial resources toward diversified fleet expansion, hyperdrive-equipped multi-role starfighters (such as the TIE Defender project), elite officer meritocracy, intelligence gathering, and cultural analysis of opposing factions to anticipate and systematically dismantle insurgencies rather than relying on indiscriminate terror.