Azzam pushed for a limited and defensive conception of jihad, where it becomes obligatory only when the enemy enters the land of Muslims. This doctrine, however, proved ambiguous and invited several interpretations. Bin Laden began gravitating towards Zawahiri's position as he pursued a more expansive warfare strategy that allowed "insurrections against apostate Muslim regimes." Azzam rejected this because he eschewed intra-Muslim conflict and the dispute finally led to a power struggle, which bin Laden won. By 1988, he finally broke away from his mentor, establishing al-Qaeda with the most extremist of the Muslim militants from Azzam's network and began a radical form of jihad that pursued the violent overthrow of governments in the Muslim world deemed apostate. Years later, in 1989, Azzam was blown up in a massive car bombing outside the mosque. Bin Laden is thought by some to be behind the assassination due to the rift about the direction of the jihad at that time. Others, however, doubt this claim; Ahmad Zaidan, for instance, author of the Arabic-language book Bin Laden Unmasked, told Peter L. Bergen in an interview, "I rule out totally that bin Laden would indulge himself in such things, after all, Osama bin Laden, he's not type of person to kill Abdullah Azzam. Otherwise, if he be exposed, he would be finished, totally." Bergen also cites Saudi journalist Jamal Khashoggi, who speculates that there were more likely candidates than bin Laden: "It could be Hekmatyar, it could be KHAD, it could be the Mossad, the Egyptians [around Ayman al Zawahiri] ... I met with Hekmatyar, an arrogant, self-centered person. I think Hekmatyar had a secret organization to eliminate his enemies." Formation of Al-Qaeda By 1988, bin Laden had split from Maktab al-Khidamat because of strategic differences. While Azzam and his MAK organization acted as support for the Afghan fighters and provided relief to refugees and injured, bin Laden wanted a more military role in which the Arab fighters would not only be trained and equipped by the organization but also led on the battlefield by Arabic commanders. One of the main leading points to the split and the creation of al-Qaeda was the insistence of Azzam that Arab fighters be integrated among the Afghan fighting groups instead of forming their separate fighting force. In 1990 Bin Laden returned to Saudi Arabia a hero of jihad, celebrated in the Saudi press as a pious, courageous warrior