A US-backed alliance of Syrian Kurdish and Arab fighters says it has seized control of the city of Raqqa, ending three years of rule by so-called Islamic State (IS).
The defeat of IS in the de facto capital of its self-styled “caliphate” is being seen as another significant victory in the battle to force the jihadist group out of Iraq and Syria.
The Syrian Democratic Forces (SDF) alliance launched its assault on Raqqa in June, a month before Iraqi pro-government forces declared that the city of Mosul had been “liberated” following a nine-month offensive with air and ground support from a US-led multinational coalition.
Iraqi forces have also recently cleared the IS strongholds of Tal Afar and Hawija, leaving the jihadists in control of a sliver of land along the Euphrates river valley in the western desert, near the border with Syria.
IS still controls large parts of the valley in the neighbouring Syrian province of Deir al-Zour, but it is under pressure there from the SDF and Syrian pro-government forces. The latter are backed by Russian air strikes and fighters from Lebanon’s Hezbollah movement.
Raqqa was the first big city captured by IS in Syria in early 2014. The group went on to seize a large swathes of the country, from the border with Iraq in the east up to Aleppo and the Turkish border in the north-west.
In Iraq, IS fighters overran Mosul in June 2014 and then moved southwards towards the capital Baghdad, routing the Iraqi army and threatening to eradicate the country’s many ethnic and religious minorities.
At its peak, some 10 million people were living in territory under IS control.
The battle for Raqqa
The Clock tower roundabout in central Raqqa where IS performed several public executions
An intensive aerial bombardment by the US-led coalition helped secure victory in Raqqa for the Syrian Democratic Forces (SDF), which was formed in 2015 by the the Kurdish Popular Protection Units (YPG) militia and a number of smaller, Arab factions. Since early June, coalition planes have carried out almost 4,000 air strikes on the city.
Estimates of the number of casualties vary. The Syrian Observatory for Human Rights, a UK-based monitoring group, said at least 3,250 people had been killed, among them 1,130 civilians. Other groups say the total was higher.
The UN estimates about 270,000 people fled their homes during the SDF offensive.
The immense task of rebuilding the city may take years. Clearing operations are already under way to uncover any jihadist sleeper cells and remove landmines.
The stadium was the hub of IS intelligence operations in Raqqa
Meanwhile, the SDF says its offensive against IS in Deir al-Zour will now accelerate, with fighters being redeployed there from Raqqa.
Rebuilding Mosul is being seen as a major challenge for the Iraqi government. One Iraqi official estimated it would cost $1bn, others have put the figure far higher.
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The top US commander in Iraq has also urged the government to “reach out and reconcile with the Sunni population” to prevent “ISIS 2.0 from emerging”.
How did IS spread across Iraq and Syria?
The jihadists exploited the chaos and divisions within both Syria and Iraq.
IS grew out of what was al-Qaeda in Iraq, which was formed by Sunni militants after the US-led invasion in 2003 and became a major force in the country’s sectarian insurgency.
In 2011, the group joined the rebellion against President Bashar al-Assad in Syria, where it found a safe haven and easy access to weapons.
At the same time, it took advantage of the withdrawal of US troops from Iraq, as well as widespread Sunni anger at the sectarian policies of the country’s Shia-led government.
In 2013, the group began seizing control of territory in Syria and changed its name to Islamic State in Iraq and the Levant (Isis or Isil).
The following year, Isis overran large swathes of northern and western Iraq, proclaimed the creation of a “caliphate”, and became known as “Islamic State”.
A subsequent advance into areas controlled by Iraq’s Kurdish minority, and the killing or enslaving of thousands of members of the Yazidi religious group, prompted the US-led coalition to begin air strikes on IS positions in Iraq in August 2014.
As IS is now being forced out of Iraq and Syria, another problem is the likely resurgence of hostilities between rival groups. Already Iraqi forces have pushed the Kurds back from land they took during the fight against IS around Kirkuk.
Exact numbers of casualties from the conflict with IS are not available.
The UN says at least 6,878 civilians were killed in acts of violence in Iraq in 2016 and more than 2,700 to the end of September this year – although the true figure is likely to be higher as the organisation has been unable to verify some reports of casualties in the Mosul area.
According to Iraq Body Count, the total number of civilian deaths in Iraq since 2014 stood at 66,345 on 8 October.
The UN no longer keeps track of casualty figures in Syria due to the inaccessibility of many areas and the conflicting reports from the various parties to the war there.
The Syrian Observatory for Human Rights, a UK-based monitoring group, reported in July 2017 that more than 475,000 people, including 99,600 civilians, had been killed since the uprising against President Bashar al-Assad began March 2011.
Who is fighting IS?
The US-led coalition has conducted more than 12,766 air strikes against IS targets in Iraq since August 2014.
Most attacks have been carried out by US aircraft, but those from Australia, Belgium, Denmark, France, Jordan, the Netherlands and the UK have also taken part.
In Syria, the air campaign began in September 2014. Since then, about 12,850 strikes have been carried out by coalition forces, which include Australia, Bahrain, France, Jordan, the Netherlands, Saudi Arabia, Turkey, United Arab Emirates and the UK.
The number of strikes each month rose steadily in Iraq up to a peak in January 2016 and then began to fall as the number of strikes in Syria increased dramatically, reaching a high of just over 1,500 in September 2017.
Russia is not part of the coalition, but its jets began air strikes against what it called “terrorists” in Syria in September 2015.
There is little information from official sources about the Russian air strikes. The Institute for the Study of War said evidence suggested Russian planes targeted deep into opposition-held territory, and helped Syrian government forces to retake control of the city of Aleppo in December 2016.
However, Russia warned the US coalition that it would treat its aircraft as targets after the US shot down a Syrian military plane during the assault on Raqqa. The incident led to a suspension of communications between the two sides aimed at avoiding clashes in the air.
Global reach of IS
With the proclamation of a caliphate at the end of June 2014, IS signalled its intention to spread beyond Iraq and Syria.
By August 2016, IS was reported to be operational in 18 countries across the world, including Afghanistan and Pakistan, according to evidence seen by the US National Counterterrorism Center. It also found signs of what it called “aspiring branches” in Mali, Egypt, Somalia, Bangladesh, Indonesia and the Philippines.
During 2016, IS also claimed attacks in a number of countries, including Egypt, Turkey, Indonesia, France, Belgium, Germany, the US and Bangladesh. In 2017, IS has claimed to be behind at least two attacks in the UK.
The proclamation of the caliphate triggered a surge in the number of foreign fighters travelling to Syria and Iraq to join IS.
According to the head of the UK’s intelligence service, MI5, more than 800 people have travelled from UK to join the conflict in Iraq and Syria – and 130 of them had died.
How does IS get its funding?
Oil was once the biggest single source of revenue for IS. The group seized control of many oil fields in Syria and Iraq, and sold oil on the black market.
But revenue has fallen since IS lost control of oil-producing areas in northern Syrian and western Iraq, and US-led coalition and Russian air strikes began targeting oil infrastructure.
Income from taxes and fees has also fallen as IS has lost control of major cities like Mosul and Raqqa.
Money obtained by looting and fines initially increased, especially when IS seized Mosul in 2014, but has since declined.
At one point, IS was reported to be so short of funds that it was imposing random fines for offences like driving on the wrong side of the road.
According to a report by IHS Markit, territorial losses are the main factor contributing to IS’s loss of revenue. It says the group’s ability to compensate for financial losses by increasing the fiscal burden on the population it controls appears to have reached its limits.
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Where are the refugees?
More than five million Syrians have fled abroad to escape the fighting in Syria, according to the UN. Most have ended up in neighbouring Turkey, Lebanon and Jordan.
About 970,000 Syrians applied for asylum in Europe between April 2011 and July 2017, according to UN figures.
The UN estimates there are more than three million Iraqis who have been forced to leave their homes to escape the conflict with IS and are displaced within the country.
The battle for control of Mosul led to about one million people fleeing their homes – about 800,000 are still living in temporary camps or with relatives.