A member of the Iraqi security forces fires artillery during clashes with ISIS militants near Falluja, Iraq, May 29, 2016.

Iraqi forces started pushing into the city of Fallujah on Monday, May 30, 2016, as a wave of bombings claimed by ISIS in Baghdad and near the Iraqi capital killed at least 24 people.

Civilians who fled their homes due to the clashes in Falluja, gather on the outskirts of Falluja, May 26, 2016.

An Iraqi soldier stands guard at the entrance of the Nineveh base for liberation operations in Makhmur, about 280 kilometers (175 miles) north of the capital Baghdad on February 11, 2016.

The Iraqi army deployed thousands of soldiers to a northern base in preparation for operations to retake the ISIS hub of Mosul, according to officials, as ISIS still holds Fallujah, east of Ramadi, and Mosul, Iraq's second city that is located in the north.

Iraqi security forces and Shi'ite fighters clash with ISIS militants in Salahuddin province, March 2, 2015.

Iraq's armed forces, backed by Shi'ite militia, attacked ISIS strongholds north of Baghdad as they launched an offensive to retake the city of Tikrit and the surrounding Sunni Muslim province of Salahuddin.

Iraqi security forces carry a wounded soldier during clashes with ISIS militants in Salahuddin province, March 2, 2015.

Iraq's armed forces, backed by Shi'ite militia, attacked ISIS strongholds north of Baghdad as they launched an offensive to retake the city of Tikrit and the surrounding Sunni Muslim province of Salahuddin.

Smoke and flames rise over the Syrian town of Kobani after an airstrike, as seen from the Mursitpinar border crossing on the Turkish-Syrian border in the southeastern town of Suruc in Sanliurfa province, Oct. 18, 2014.

A U.S.-led military coalition has been bombing Islamic State fighters who hold a large swathe of territory in both Iraq and Syria, two countries involved in complex multi-sided civil wars in which nearly every country in the Middle East has a stake.

Iraqi Shiite men who have volunteered to join government forces and militias in the fight against jihadists from the Islamic State group, take part in a training session in the central city of Hillah, Iraq, Oct. 18, 2014.

Shiite Iraqi fighters, loyal to Grand Ayatollah Ali al-Sistani, fire missiles from a launcher during clashes with Islamic State militant group fighters in Jurf al-Sakher, north of the Shiite shrine city of Karbala, Oct. 19, 2014.

Iraqi security forces and civilians gather at the site of a car bomb attack in Baghdad, Oct. 21, 2014.

A series of bombs targeting restaurants across Baghdad killed at least 21 people, police and medics said. The Iraqi capital has witnessed a surge in bombings over the past month, most claimed by Islamic State militants who have overrun large parts of Iraq and neighbouring Syria.

Turkish Kurds warm themselves around an open fire as they watch the Syrian town of Kobani, near the Mursitpinar border crossing, on the Turkish-Syrian border in the southeastern town of Suruc in Sanliurfa province, Oct. 21, 2014.

Smoke and flames rise over a hill near the Syrian town of Kobani after an airstrike, as seen from the Mursitpinar crossing on the Turkish-Syrian border in the southeastern town of Suruc in Sanliurfa province, Oct. 23, 2014.

U.S. military forces again focused air strikes on the area near the Syrian city of Kobani in their campaign to turn back Islamic State forces and also hit oil facilities held by the militant group, the U.S. Central Command said on Thursday.

A man holds up a knife as he rides on the back of a motorcycle touring the streets of Tabqa city with others in celebration after Islamic State militants took over Tabqa air base, in nearby Raqqa city, Aug. 24, 2014.

ISIS militants stormed the air base in northeast Syria on Sunday, capturing most of it from government forces after days of fighting over the strategic location, a witness and a monitoring group said.

A member loyal to the Islamic State in Iraq and the Levant (ISIS) waves one of their flags in Raqqa, Syria, June 29, 2014.

Iraqi Kurdish Peshmerga fighters fire at ISIS militant positions, from their position on the top of Mount Zardak, a strategic point about 15 miles east of Mosul, Sept. 9, 2014.

Iraqi Shiite militia fighters hold the ISIS flag as they celebrate after breaking the ISIS siege of Amirli with the help of U.S. airstrikes, Sept. 1, 2014.

A fighter of the Islamic State of Iraq and Syria, or ISIS, waves the group's flag from inside a captured government fighter jet following the battle for the Tabqa air base, in Raqqa, Syria, in this undated image posted Aug. 27, 2014, by the Raqqa Media Center of ISIS.

An ISIS militant uses a loud-hailer to announce to residents of Taqba city that Tabqa air base has fallen to Islamic State militants, in nearby Raqqa city, Aug. 24, 2014.

Undated image posted by Raqqa Media Center, a Syrian opposition group, on June 30, 2014, which shows fighters from the Islamic State of Iraq and Syria (ISIS) during parade in Raqqa, Syria.

This undated file picture released on Wednesday Jan. 29, 2014, by the official website of Iraq's Interior Ministry claims to show Abu Bakr al-Baghdadi, the head of the so called Islamic State of Iraq and the Levant (ISIS). While his may not be a household name, Al-Baghdadi has emerged as one of the world's most lethal terrorist leaders. He is a renegade within al-Qaida whose maverick streak eventually led its central command to sever ties, deepening a rivalry between his organization and the global terror network.

Sailors launch aircraft from the flight deck of the aircraft carrier USS George H.W. Bush (CVN 77), Aug. 7, 2014. George H.W. Bush is supporting maritime security operations and theater security cooperation efforts in the U.S. 5th Fleet area of responsibility.

Smoke rises after airstrikes targeting Islamic State militants near the Khazer checkpoint outside of the city of Erbil in northern Iraq, Aug. 8, 2014. Iraqi Air Force has been carrying out strikes against the militants, and for the first time on Friday, U.S. war planes have directly targeted the extremist group ISIS, which controls large areas of Syria and Iraq.

A fighter with ISIS directs a vehicle with a Christian family to leave from their home village outside Erbil, northern Iraq, Aug. 7, 2014.

Militants from the Islamic State of Iraq and Syria celebrate the group's declaration of an "Islamic State," in Fallujah, 40 miles west of Baghdad, June 30, 2014.

Iraqi security forces and armed volunteers move with military vehicles during clashes with militants of the Islamic State of Iraq and Syria (ISIS), in the town of Dalli Abbas near Baghdad, July 3, 2014.

ISIS loyalists wave ISIS flags as they drive around Syrian city of Raqqa, June 29, 2014

A U.S. Geological Survey satellite image shows smoke rising from the Baiji refinery near Tikrit, Iraq, June 18, 2014 in this handout provided by U.S. Geological Survey. President Barack Obama said on Thursday he was sending up to 300 U.S. military advisers to Iraq but stressed the need for a political solution to the Iraqi crisis as government forces battled Sunni rebels for control of the country's biggest refinery. Image taken June 18, 2014.

This undated file image posted on a militant website on Jan. 4, 2014, which is consistent with other AP reporting, shows Shakir Waheib, a senior member of ISIS, left, next to a burning police vehicle in Iraq's Anbar Province. Led by Abu Bakr al-Baghdadi, ISIS is the main driver of destabilizing violence in Iraq and until recently was the main al-Qaida affiliate there. Al-Qaida's general command formally disavowed the group this week, saying it "is not responsible for its actions."

A fighter of the Islamic State of Iraq and Syria (ISIS) stands guard at checkpoint near the city of Baiji, north of Baghdad, June 19, 2014.

Volunteers who have joined the Iraqi army to fight against predominantly Sunni militants from the radical Islamic State of Iraq and Syria (ISIS), carry weapons during a parade in the streets in Al-Fdhiliya district in eastern Baghdad, June 15, 2014.

Kurdish Iraqi Peshmerga forces deploy their troops and armored vehicles on the outskirts of the multi-ethnic city of Kirkuk, only 1 kilometer away from areas controlled by Sunni Muslim jihadists from the Islamic State of Iraq and Syria (ISIS) on the main road between Kirkuk, Mosul and Baiji in northern Iraq, June 12, 2014.

Female members of the Kurdistan Workers' Party (PKK) take position on the front line in Makhmur, some 50 km south of Erbil, the capital of the autonomous Kurdish region of northern Iraq where clashes with Islamic State (IS) militants are ongoing, Aug. 9, 2014. Makhmur, is one of the areas that had been attacked by jihadist fighters in recent days. After a first day of US air raids on fighters who had moved within striking distance of Kurdistan, a top official in the autonomous region said the time had come for a fightback.

A Female member of the Kurdistan Workers' Party (PKK) holds her equipment as she takes position on the front line in Makhmur, some 50 km south of Erbil, the capital of the autonomous Kurdish region of northern Iraq where clashes with Islamic State (IS) militants are ongoing on August 9, 2014. Makhmur, is one of the areas that had been attacked by jihadist fighters in recent days. After a first day of US air raids on fighters who had moved within striking distance of Kurdistan, a top official in the autonomous region said the time had come for a fightback.

Peshmerga fighters stand guard at Mosul Dam in northern Iraq, Aug. 21, 2014. Despite its structural faults, the country's biggest dam at 3.6 km long, built by a German-Italian consortium in the 1980s, is a vital water and power source for Mosul, Iraq's largest northern city of 1.7 million residents. Control the dam and you control the 'keys' to the city. With that in mind, Islamic State insurgents who captured swathes of Iraq and Syria and declared a caliphate, wrested control of the dam from Kurdish forces in recent weeks. While Iraqi and Kurdish forces recaptured the dam with the help of U.S. air strikes on Monday, "the most dangerous dam in the world" - as a U.S. Army Corps of Engineers report described it - still has the potential for catastrophe.