On the night of June 22 or 23, 1139, the then atabeg of Damascus Shihab al-Din Mahmud was assassinated by three of his pages.
Minister Mu'in al-Din Unur then took matters in hand energetically, had the assassins crucified and brought Prince Jamal al-Din Muhammad, half-brother of the deceased atabeg and emir of Baalbek, to Damascus to do so.
[1] In the meantime, the mother of Mahmud, since remarried in Zengi, called her husband for help, who ran hoping to seize Damascus, but the dispositions of Mu'in al-Din Unur took him by surprise, and he can only lay siege to Baalbek on August 20, 1139.
The citadel resists so well that, when the garrison surrenders, on October 21, Zengi orders the soldiers to be crucified despite his oaths to spare them, hoping to frighten the Damascenes, but it only strengthens the determination of the population around its leaders.
Zengi established his camp near Damascus on December 6, 1139, and following a success against the Damascene troops on December 21 again proposed the exchange of Damascus for Homs or Baalbek, a proposal that the young atabeg thought he would accept, but Unur takes it upon himself to dissuade him, citing Zengi's disloyalty.