He attracted the attention of an Abbasid caliph by conquering non-Muslim territories in the east, which are now mostly part of modern Afghanistan/Pakistan. Then he began acting as an independent ruler and eventually succeeded in gaining control of much of what is now Iran, Afghanistan and large parts of Pakistan. He became the sovereign monarch of the first Iranian dynasty after the Arab Islamic conquest. In many cases, the people he conquered had rebelled against their Islamic overloards and reverted to prior forms of worship.
From his capital Zaranj, he conquered a vast area that included: Kabul Valley, Sind, Tocharistan, Makran (Baluchistan), Kerman, Fars, Khorasan. He attempted to conquer Baghdad but was defeated by the forces of the caliph al-Mu'tamid. It was during his rule that Persian was introduced as an official language, ending the pervasive influence of the Arabic language. Laith has been accorded the historical status of a popular folk hero in history because his court began the revitalization of the Persian language after two centuries of domination by the Arabic language.