Activists with Jabhat al-Nusra FlagWriting for Al Jazeera English, Basma Atassi, claims that the head of Al Qa'eda, Ayman al-Zawahari, has intervened in a dispute between the Syrian insurgency Jabhat al-Nusra and the Islamic State of Iraq with a letter to the leaders of the two groups. The clash arose in April when the head of the ISI, Abu Bakr al-Baghdadi, tried to claim oversight of Jabhat al-Nusra in a message. A senior JAN commander, Abu Muhammad al-Joulani, responded by asserting the insurgents' autonomy in Syria. Instead, the challenge for Jabhat al-Nusra was that --- even as it tried to maintain indpendence from the Iraqi faction --- its fighters might join ISI. So, according to Atassi, al-Joulani sent a letter to Zawahiri to arbitrate between the two groups.