 In the 18th century, the steady weakening of the Shamkhals fostered the ambitions of the Avar khans, whose greatest coup was the defeat of the 100,000-strong army of Nader Shah in September 1741 during his conquest of Dagestan.In the wake of this success, Avar sovereigns managed to expand their territory at the expense of free communities in Dagestan and Chechnya.The reign of Umma-Khan (from 1775 to 1801) marked the zenith of the Avar ascendancy in the Caucasus.