A number of them met in Mecca and discussed the 659 Battle of Nahrawan, which took place as a consequence of Siffin, wherein most of their men were eradicated while facing Ali's army. They concocted a plot to assassinate three prominent Muslim personalities: Amr ibn Bakr al-Tamimi was to kill 'Amr ibn al-'As, al-Hujjaj al-Tamimi was to kill Mu'awiya ibn Abu Sufyan and ibn Muljam was tasked to kill the caliph, Ali.
A number of them gathered in Mecca and discussed the Battle of Nahrawan, which was a consequence of Siffin, where most of their men were killed while fighting against Ali's army. They devised a plan to assassinate three prominent Muslim figures: Amr ibn Bakr al-Tamimi was assigned to kill 'Amr ibn al-'As, al-Hujjaj al-Tamimi was tasked with killing Mu'awiya ibn Abu Sufyan and ibn Muljam was ordered to eliminate the caliph, Ali.