Key players in the battle for Iraq
Islamic State of Iraq and Syria: The jihadist group, an offshoot of al-Qaida, has a fighting force that is probably larger than the 10,000 or so members estimated in most reports. They are well-armed and have boosted their arsenal after looting equipment from Mosul's main army bases. Sometimes referred to as the Islamic State of Iraq and the Levant.
Abu Bakr al-Baghdadi: The Iraqi-born leader of ISIS, who has a $10 million U.S. bounty on his head, has been described as "the new bin Laden" by Time magazine and, while a deadly ideologue, has managed to assemble an incredibly cohesive, capable outfit that is well-funded and well-armed.
Kurds: The autonomous government in the Iraqi region of Kurdistan has rallied its own forces, known as the pesh merga, to combat ISIS. Although the Kurds have had an adversarial relationship with Baghdad, reports suggest that they are now more closely coordinating efforts to counter ISIS. They possess some light armored vehicles as well as artillery and will probably be the key to winning back Mosul.
Prime Minister Nouri al-Maliki: Iraq's premier rose to prominence in the wake of the U.S. invasion and, as a leader of a prominent Shiite political party, assembled the government in 2006. He has managed to remain in power, but presides over a deeply polarized political landscape. Critics accuse his government of marginalizing the country's Sunnis while strengthening his political base.
Grand Ayatollah Ali al-Husseini al-Sistani: Iraq's top Shiite cleric, who is 83 years old. His statements carry enormous weight among not just the Shiite majority but members of other groups including some Sunnis. On Friday, Sistani called on Iraqis to take up arms to combat the marauding Sunni extremist militants. Within hours, thousands of Iraqi Shiites responded to the call.
Iran: The Shiite state looks upon developments in Iraq with great concern. ISIS is a foe, and its success in Syria and Iraq is an existential challenge to two staunch allies of Tehran. On Thursday, reports emerged that two battalions of the Quds Force, the overseas wing of Iran's Revolutionary Guards, were in Iraq, helping the government battle ISIS.