Although they worked together nominally, the central Al Qaeda network, as led by Osama bin Laden and Ayman al-Zawahiri, and the late Abu Musab al-Zarqawi's terrorist group in Iraq held vastly different conceptions of jihad. The U.S. invasion and occupation of Iraq minimized the magnitude of that ideological clash, enabling Zarqawi's limited cooperation with Al Qaeda in the Iraqi arena. Although they used each other for tactical support, publicity, and recruiting purposes, their doctrinal differences made them only allies of convenience rather than genuine partners, and as Zarqawi's tactics grew more extreme and indiscriminate, Al Qaeda chose to distance itself from his handiwork. The U.S. air strike that killed Zarqawi on June 7, 2006, deprived Al Qaeda in Iraq (AQI) of its strategic leader. But the knowledge that U.S., Iraqi, and Jordanian intelligence effectively penetrated AQI to gather information on Zarqawi's whereabouts is just as important to the group's future as Zarqawi's elimination. The coalition ' demonstrated ability to gather accurate intelligence is likely to frighten and sow distrust among AQI's remaining members. This heightens the leadership challenge for AQI's new emir, identified only under the alias Abu Hamzah al-Muhajir. His response to the internal security questions and the lingering doctrinal impasse with Al Qaeda proper will determine the organization's future trajectory. The challenge for Muhajir is to strike a balance between appealing to secular and tribal Sunnis in Iraq, some of whom likely provided intelligence that helped doom Zarqawi, while maintaining an insular terrorist network that can sustain potentially weakening criticism from Islamic, Arab, and Western sources.