Richard A. Falkenrath says that with Osama bin Laden gone, life is about to become more complicated for U.S. policymakers trying to combat terrorism.

Shiite-Sunni relations have become frayed since the war in Iraq and the rise of Sunni insurgents like Abu Musab al-Zarqawi. The outcome of the war will have widespread consequences for the future of Islam's followers.

Steven Simon and Jonathan Stevenson argue that demilitarizing Hezbollah is crucial to rolling back Iranian influence in the Middle East and shaping an environment more conducive to Arab-Israeli accomodation.

Imad Mughniyeh's killing “was the first major attack against a Hezbollah leader since Israel assassinated the group’s secretary-general in 1992,” reports Mohamad Bazzi.

CFR's Elliott Abrams discusses the implications of Osama bin Laden's death for the future of al-Qaeda and the evolving democracy movements in the Arab world.

Listen to John B. Bellinger III, Steven Simon, and Lydia Khalil consider the ramifications of the Justice department's controversial decision to prosecute suspected September 11th mastermind, Khalid Sheik Mohammed, and his four alleged co-conspirators.

A profile of Hassan Nasrallah, the secretary-general of Hezbollah.

Examining the life and tactics of Imad Fayez Mugniyah, the Hezbollah military mastermind killed in Damascus on February 13, 2008. Before 9/11, Mugniyah was said to be responsible for the deaths of more Americans than any other terrorist.

Chechen separatist Shamil Basayev is one of several rebel leaders to die violently in recent years. His death leaves the future of the movement in doubt.

From his exile in Syria, Khaled Meshal, the top ranked member of Hamas, exercises leadership and serves as the group's diplomatic envoy.

Five days after U.S. forces killed al-Qaeda in Iraq leader Abu Musab al-Zarqawi, the group announced his successor, the unknown Abu Hamza al-Muhajir. Speculation abounds about the man and the significance of his appointment.

The death of Abu Musab al-Zarqawi, Iraq's most wanted man, is an important event but one unlikely to affect the insurgency greatly.

A profile of Abu Bakar Bashir, the Indonesian cleric whose fiery invectives have motivated terrorist attacks like the 2002 Bali bombings, and who some experts say is affiliated with al-Qaeda.

A profile of the terrorist Abu Musab al-Zarqawi, the man responsible for coordinating suicide bombings in Amman and Madrid, multiple attacks on Iraqi Shiites and Shiite mosques, and the highly-publicized beheading of American Nicholas Berg.

A profile of Osama bin Laden, founder and leader of al-Qaeda.

The threat posed by the al-Qaeda-Taliban relationship is a crucial element in U.S. strategic planning in Afghanistan. Four experts explore the changing nature of these sometimes murky ties.

Mohamad Bazzi, former Middle East correspondent for Newsday, says evidence suggests Israel’s intelligence agents as the most likely source of the bomb that killed Hezbollah terrorist chief Imad Mugniyah, but other scenarios also are feasible.