Salih launched his career in 1008, when he seized the Euphrates river fortress of al-Rahba. In 1012, he was imprisoned and tortured by the emir of Aleppo, Mansur ibn Lu'lu'. Two years later he escaped, capturing Mansur in battle and releasing him for numerous concessions, including half of Aleppo's revenues. This cemented Salih as the paramount emir of his tribe, the Banu Kilab, many of whose chieftains had died in Mansur's dungeons. With his Bedouin warriors, Salih captured a string of fortresses along the Euphrates, including Manbij and Raqqa, by 1022. He later formed an alliance with the Banu Kalb and Banu Tayy tribes and supported their struggle against the Fatimids of Egypt. During this tribal rebellion, Salih annexed the central Syrian towns of Homs, Baalbek and Sidon, before conquering Fatimid-held Aleppo in 1025, bringing "to success the plan which guided his Kilab forebears for a century", according to historian Thierry Bianquis.