Hephthalite Empire
The Kushans ruled the area as part of their larger empire until the 3rd century AD, when the Zoroastrian Persian Sassanid Empire invaded Kushan territory from the southwest. Fergana remained under shifting local and Transoxian rulers thereafter. For periods in the 4th and 5th centuries, the Sassanid Empire directly controlled Transoxiana and Fergana, led by the conquests of Shapur II and Khosrau I against the Kushans and the Hephthalite Empire.