Who is Gen. Dugal Tennar and Col. Hender Linn from Forward the Foundation and what is their importance?

Gen. Dugal Tennar and Col. Hender Linn are the newest head of the military junta that for a decade rules the Empire after Emperor Cleon I's assassination and Hari Seldon's retirement from the office of First Minister, Tennar establishes a reputation for ignorance, superstition, and violence on Mandanov before rising to the top. Senior Mathematician Tamwile Elar, also from Mandanov, warns Hari about him before a meeting and Dors Venabili calls Tennar a monster. Tennar is a stocky man with a carefully-clipped, reddish mustache and cold blue eyes. He has grown pudgy. He lives in secure but rundown housing on the outskirts of the Palace grounds, but yearns to occupy the Small Palace and establish a dynasty of his own.