Retired Dutch General Patrick Cammaert (2nd R), who heads a United Nations advance team tasked with monitoring a ceasefire between the Iranian-aligned Houthi group and Saudi-backed government forces in Yemen's Hodeidah, walks upon his arrival in Aden, Yemen December 22, 2018. REUTERS/Fawaz Salman 

Sadeq Amin Abou Rass (2nd R) who was picked to succeed Yemen's slain former president Ali Abdullah Saleh as a leader of the General People's Congress party, attends a meeting of the party's leadership in Sanaa, Yemen January 7, 2018. REUTERS/Khaled Abdullah 

Nahla Arishi (2nd R), a pediatrician, talks to relatives of a boy infected with diphtheria at the al-Sadaqa teaching hospital in the southern port city of Aden, Yemen December 18, 2017. Picture taken December 18, 2017. To match Special Report YEMEN-DIPHTHERIA/ REUTERS/Fawaz Salman 

Saida Ahmed Baghili (2nd L), 19, who is recovering from severe malnutrition, poses for a photograph with her father and her sisters Jalila (L), 12, and Amal (R), 7, and 4-year-old brother Omar (4th L) at their hut in al-Tuhaita district of the Red Sea province of Hodeidah, Yemen, October 20, 2017. REUTERS/Abduljabbar Zeyad SEARCH "ZEYAD BAGHILI" FOR THIS STORY. SEARCH "WIDER IMAGE" FOR ALL STORIES. 

Lieutenant General Abdul Ghani al-Assadi (2nd L), a commander of the Counter Terrorism Service (CTS), tours the frontline in western Mosul, Iraq, April 25, 2017. REUTERS/Ahmed Jadallah 

United Nations Secretary General Antonio Guterres (2nd L) visits displaced Iraqis who fled Mosul, at Hasansham camp, in Khazer, Iraq March 31, 2017. REUTERS/Suhaib Salem 

Iraqi newlyweds, who fled Mosul, Hussain Zeeno Zannun (2nd R), 26, and Chahad, 16, watch a woman dance during their wedding party inside their tent at Khazer camp, Iraq February 16, 2017. REUTERS/Zohra Bensemra 

Iraqi newlyweds, who fled Mosul, Hussain Zeeno Zannun (2nd R), 26, and Chahad, 16, listen to the cleric advises after he conducted the religious marriage procedure outside a restaurant near Khazer camp, Iraq February 16, 2017. REUTERS/Zohra Bensemra 

Iraqi newlyweds, who fled Mosul, Hussain Zeeno Zannun (2nd R), 26, and Chahad, 16, walk during their wedding party at Khazer camp, Iraq February 16, 2017. REUTERS/Zohra Bensemra 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division play poker at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division gather around an artillery at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. Army Colonel Patrick Work, commander of the 2nd Brigade, 82nd Airborne Division, speaks during an interview with Reuters at a military base north of Mosul, Iraq February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division walk inside a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division clean the barrel of the artillery at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. Army Colonel Patrick Work, commander of the 2nd Brigade, 82nd Airborne Division, speaks during an interview with Reuters at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division train at a makeshift gym at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

A U.S. soldier from the 2nd Brigade, 82nd Airborne Division stands guard at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division gather around an artillery at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division clean the barrel of artillery at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division play poker at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

U.S. soldiers from the 2nd Brigade, 82nd Airborne Division train at a makeshift gym at a military base north of Mosul, Iraq, February 14, 2017. Picture taken February 14, 2017. REUTERS/Khalid al Mousily 

Azad Hassan (2nd R) and his brother Mohammad, whose hands were chopped off by Islamic State militants, stand beside their wounded father in a house at Nimrud village, south of Mosul, Iraq, December 13, 2016. Picture taken December 13, 2016. REUTERS/Mohammed Salem 

An Iraqi father (2nd L) mourns as soldiers carry the body of his son, who was killed during clashes in the Islamic State stronghold of Mosul, in al-Samah neighborhood, Iraq December 1, 2016. REUTERS/Mohammed Salem 

Zarifa Badoos Daddo (2nd L), 77, speaks during an interview with Reuters in Erbil, Iraq October 30, 2016. Zarifa was reunited with her family on Sunday after Iraqi forces drove Islamic State from the town of Qaraqosh, southeast of Mosul, Iraq. Picture taken October 30, 2016. REUTERS/Azad Lashkari

Massoud Barzani President of Iraq Kurdish Region (2 nd L) receives President of the Natonal alliance, a coalition of Shiite political group, Ammar Hakim at Zartac Mountain near Nineveh, Iraq October 27, 2016. REUTERS/Azad Lashkari 

UNICEF Middle East and North Africa Regional Director Geert Cappelaere (2nd R) visits a Debaga camp for displaced people on the outskirts of Erbil, Iraq October 23, 2016. REUTERS/Thaier Al-Sudani 

Iraqi Prime Minister Haider al-Abadi (2nd R) shakes hands during his visit in Kirkuk, Iraq, October 14, 2016. REUTERS/Ako Rasheed 

U.N. special envoy for Yemen Ismail Ould Cheikh Ahmed (2nd L) meets officials upon his arrival at Sanaa airport July 13, 2016. REUTERS/Khaled Abdullah 

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool TPX IMAGES OF THE DAY

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool TPX IMAGES OF THE DAY

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, arrives to deliver a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, arrives to deliver a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Former British Prime Minister, Tony Blair, delivers a speech following the publication of The Iraq Inquiry Report by John Chilcot, in London, Britain July 6, 2016. REUTERS/Stefan Rousseau/Pool 

Peter Brierley, Matthew Jury and Roger Bacon, relatives of military personnel killed during the Iraq War speak at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Relatives and friends of military personnel killed during the Iraq War attend a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Relatives and friends of military personnel killed during the Iraq War attend a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Peter Brierley, Matthew Jury, Roger Bacon and Roger Keys, relatives of military personnel killed during the Iraq War speak at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Relatives and friends of military personnel killed during the Iraq War attend a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Roger Bacon, a relative of military personnel killed during the Iraq War speaks at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Dan Kitwood/Pool 

Peter Brierley, Matthew Jury, Roger Bacon, Roger Keys, Rose Gentle and Sarah O'Connor, relatives of military personnel killed during the Iraq War speak at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Roger Keys, Rose Gentle and Sarah O'Connor, relatives of military personnel killed during the Iraq War, speak at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Jeff J Mitchell/Pool 

Rose Gentle and Sarah O'Connor, relatives of military personnel killed during the Iraq War react at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Dan Kitwood/Pool 

Peter Brierley, Matthew Jury, Roger Bacon, Roger Keys, Rose Gentle and Sarah O'Connor, relatives of military personnel killed during the Iraq War, speak at a news conference after listening to Sir John Chilcot present The Iraq Inquiry Report at the Queen Elizabeth II Centre in Westminster, in London, Britain July 6, 2016. REUTERS/Dan Kitwood/Pool 

Iraq's Prime Minister Haider al-Abadi (front 2nd L) walks during his visit to an Iraqi army base in Camp Tariq near Falluja, Iraq, June 1, 2016. REUTERS/Alaa Al-Marjani. TPX IMAGES OF THE DAY

Iraqi Kurdish female fighter Haseba Nauzad (2nd R), 24, and Yazidi female fighter Asema Dahir (3rd R), 21, aim their weapon during a deployment near the frontline of the fight against Islamic State militants in Nawaran near Mosul, Iraq, April 20, 2016. When Islamic State swept into the northern Iraqi town of Sinjar in 2014, a few young Yazidi women took up arms against the militants attacking women and girls from their community. The killing and enslaving of thousands from Iraq's minority Yazidi community focused international attention on the group's violent campaign to impose its radical ideology and prompted Washington to launch an air offensive. It also prompted the formation of this unusual 30-woman unit made up of Yazidis as well as Kurds from Iraq and neighbouring Syria. For them, only one thing matters: revenge for the women raped, beaten and executed by the jihadist militants. REUTERS/Ahmed Jadallah SEARCH "WOMEN NAWARAN" FOR THIS STORY. SEARCH "THE WIDER IMAGE" FOR ALL STORIES 

Iraqi Kurdish female fighter Haseba Nauzad (2nd R), 24, sits next to other fighters at a site near the frontline of the fight against Islamic State militants in Nawaran near Mosul, Iraq, April 20, 2016. When Islamic State swept into the northern Iraqi town of Sinjar in 2014, a few young Yazidi women took up arms against the militants attacking women and girls from their community. The killing and enslaving of thousands from Iraq's minority Yazidi community focused international attention on the group's violent campaign to impose its radical ideology and prompted Washington to launch an air offensive. It also prompted the formation of this unusual 30-woman unit made up of Yazidis as well as Kurds from Iraq and neighbouring Syria. For them, only one thing matters: revenge for the women raped, beaten and executed by the jihadist militants. REUTERS/Ahmed Jadallah SEARCH "WOMEN NAWARAN" FOR THIS STORY. SEARCH "THE WIDER IMAGE" FOR ALL STORIES 

Iraqi Kurdish female fighter Haseba Nauzad (2nd R), 24, holds her weapon as she is surrounded by comrades at a site during a deployment near the frontline of the fight against Islamic State militants in Nawaran near Mosul, Iraq, April 20, 2016. When Islamic State swept into the northern Iraqi town of Sinjar in 2014, a few young Yazidi women took up arms against the militants attacking women and girls from their community. The killing and enslaving of thousands from Iraq's minority Yazidi community focused international attention on the group's violent campaign to impose its radical ideology and prompted Washington to launch an air offensive. It also prompted the formation of this unusual 30-woman unit made up of Yazidis as well as Kurds from Iraq and neighbouring Syria. For them, only one thing matters: revenge for the women raped, beaten and executed by the jihadist militants. REUTERS/Ahmed Jadallah SEARCH "WOMEN NAWARAN" FOR THIS STORY. SEARCH "THE WIDER IMAGE" FOR ALL STORIES 

U.N. special envoy to Yemen Ismail Ould Cheikh Ahmed (R) and UN spokesperson Charbel Raji (2nd R) attend a press conference after the first direct meeting between Yemen's warring factions, at the Kuwait Ministry of Information in Kuwait City April 22, 2016. REUTERS/Stephanie McGehee

Head of the Badr Organisation Hadi al-Amiri (2nd R) stands with Shi'ite fighters during a military operation in the west of Samarra, in the desert of Anbar, March 7, 2016. REUTERS/Thaier Al-Sudani 

People help a woman (2nd L) as she leaves her house after it was destroyed by a Saudi-led air strike in Yemen's capital Sanaa September 5, 2015. REUTERS/Mohamed al-Sayaghi 

Peter Maurer (2nd R), president of the International Committee of the Red Cross, listens to an explanation as he tours a site which the Houthi-led authorities say was hit by a Saudi-led air strike at the old quarter of Yemen's capital Sanaa August 9, 2015. The Saudi-led coalition denies that an air-strike last month destroyed four houses at the site. REUTERS/Khaled Abdullah 

U.S. Defense Secretary Ash Carter stands with Col. Otto Liller, commander, 1st Special Forces Group (Airborne) (2nd R) as he observes Iraqi Counter Terrorism Service forces participate in a training exercise at the Iraqi Counter Terrorism Service Academy on the Baghdad Airport Complex in Baghdad, Iraq, July 23, 2015. U.S. Defense Secretary Carter made a surprise visit to Baghdad on Thursday to assess the campaign against Islamic State, as Iraq advances plans to retake the fallen capital of Sunni-dominated Anbar province. REUTERS/Carolyn Kaster/Pool 

U.S. Defense Secretary Ash Carter (R) and Iraqi Gen. Taleb Shegati Al-Kenani, the commander of the Counter Terrorism Service (2nd R) look over diagrams and maps at the Combined Joint Operations Center in Baghdad, Iraq July 23, 2015. Carter made a surprise visit to Baghdad on Thursday to assess the campaign against Islamic State, as Iraq advances plans to retake the fallen capital of Sunni-dominated Anbar province. REUTERS/Carolyn Kaster/Pool 

Iraq's Prime Minister Haidar al-Abadi (2nd R) walks near a F-16 fighter jet, during an official ceremony to receive four of these aircrafts from the U.S., at a military base in Balad, Iraq, July 20, 2015. REUTERS/Thaier Al-Sudani 

Iraqi Minister of Tourism Adel Shirshab (R) and U.S. ambassador to Iraq Stuart Jones (2nd R) look at recovered artefacts during a ceremony at the National Museum of Iraq in Baghdad, July 15, 2015. The U.S. handed back to Iraq on Wednesday antiquities it said it had seized in a raid on Islamic State fighters in Syria, saying the haul was proof the militants were funding their war by smuggling ancient treasures. The Iraqi relics were captured by U.S. special forces in an operation in May against an Islamic State commander known as Abu Sayyaf. They included ancient cylindrical stamps, pottery, metallic bracelets and other jewellery, and glass shards from what appeared to be a coloured vase. REUTERS/Thaier Al-Sudani