A cikin 644, al-'Ala' ya sake kai hari Fars daga Bahrain, har zuwa Estakhr, har sai da gwamnan Farisa (marzban) na Fars, Shahrag ya fatattake shi.Bayan wani lokaci, Uthman bn Abi al-As ya sami nasarar kafa sansanin soji a Tawwaj, kuma nan da nan ya ci Shahrag ya kashe shi a kusa da Rew-shahr.A shekara ta 648, Abd-Allah bn al-Ash'ari ya tilasta wa gwamnan Estakhr, Mahak, ya mika birnin.Sai dai daga baya mazauna birnin za su yi tawaye a shekara ta 649/650 yayin da sabon gwamnan da aka nada, Abd-Allah bn Amir yake kokarin kama Gor.An yi nasara akan Gwamnan Soja na Estakhr, Ubaid Allah bn Ma'mar, aka kashe shi.A shekara ta 650/651, Yazdegerd ya tafi can don shirya wani shiri na gwagwarmaya da Larabawa, kuma, bayan wani lokaci, ya tafi Gor.Duk da haka, Estakhr ya gaza yin tsayin daka mai ƙarfi, kuma ba da daɗewa ba Larabawa suka kore su, suka kashe sama da masu kare 40,000.Daga nan sai Larabawa suka yi gaggawar kwace Gor, Kazerun da Siraf, yayin da Yazdegerd ya gudu zuwa Kerman.Mallakar musulmi a Fars ya kasance mai girgiza na wani lokaci, tare da tawaye da dama na cikin gida bayan cin nasara.