The lightning rise of Islamic State (IS), the jihadist militant group that has seized large parts of Syria and Iraq since 2014, has sent shockwaves around the Middle East and worldwide.
It is notoriously brutal, inflicting mass killings, abductions and beheadings on the people living in the areas it controls. In November 2015 it claimed responsibility for the attacks in Paris which saw 130 people killed.
A US-led coalition of countries to fight IS began air strikes in Iraq in August 2014 and in Syria a month later.
According to the US Department of Defence, the following countries have participated alongside the US in coalition air strikes against IS in Iraq: Australia, Belgium, Canada, Denmark, France, Jordan, the Netherlands and the UK.
The US says these countries have carried out strikes against IS in Syria: Australia, Bahrain, Canada, France, Jordan, Saudi Arabia, Turkey and the United Arab Emirates (UAE).
Separately, Russia began carrying out air strikes in Syria in September 2015 after a request from Syrian President Bashar al-Assad, who has clung on to power despite more than four years of civil war
We look at where key countries in the region and beyond stand.
Regional Sunni power Saudi Arabia is part of US-led military action against IS targets in Syria.
Riyadh also agreed to a US request to provide a base to train moderate Syrian rebel forces. The kingdom has been a key supporter of the rebels, including hardline Islamist groups, but it has rejected an Iranian accusation that it has directly supported IS. However, wealthy Saudis have sent donations to the group and some 2,500 Saudi men have travelled to Syria to fight.
The Saudi authorities are concerned that IS will inspire Saudi jihadists to challenge the monarchy’s legitimacy and seek to overthrow it.
In July 2014, Riyadh deployed 30,000 troops to beef up security along its border with Iraq, and the following month hosted Iran’s deputy foreign minister as the two regional rivals agreed to co-operate.
Jordan, a staunch US ally, said it had joined the US and several Gulf Arab states in carrying out air strikes on IS militants in Syria in September 2014 to “ensure the stability and security” of its borders.
A government spokesman said it took action in order to “pre-empt danger before it arrived in our country”, and that he believed the Jordanian public would understand the need to forestall the jihadist group before it became active in Jordan.
IS has threatened to “break down” Jordan’s borders and the group enjoys the support of a growing number of people in the kingdom, some of whom staged demonstrations in the southern town of Maan in June 2014. More than 2,000 Jordanian citizens are believed to have travelled to Syria to fight in the past three years.
Before launching the air strikes on IS, the Jordanian military had doubled its military presence along the border with Iraq.
The killing of Jordanian pilot Moaz al-Kasasbeh, captured by IS in December 2014, appears to have strengthened the government’s resolve to take on the militants, with King Abdullah II saying his death would not be in vain and promising a “severe response”.
Regional Shia power Iran has seen IS – which regards Shia as heretics who should be killed – advance to within 25 miles (40km) of its border.
Although Iran stands on the opposite side of much of the international community over Syria, it has called for co-operation against IS. It has reached out to its rival Saudi Arabia – the leading Sunni power – and turned a blind eye to US actions in Iraq, which it has historically opposed.
Officially Iran denies it has deployed any combat troops in Syria, but in June 2015, the official Irna news agency said at least 400 Iranian and Iran-based Afghan “volunteers” had been killed in the past four years.
In Iraq, the Iranians have played a key role in countering IS. Revolutionary Guards have advised Iraqi security forces, Iranian pilots have carried out air strikes, and Iranian-backed Shia militia have been mobilised.
Iran says it has also been sending weapons and advisers to Iraqi Kurdistan. In addition, Tehran joined Washington in withdrawing support for then-Iraqi Prime Minister Nouri Maliki in August 2014.
The former Shia-dominated government of Nouri Maliki marginalised Iraq’s Sunni community, creating conditions which helped the extremist Sunni IS come to prominence.
When IS overran the northern city of Mosul in June 2014 before moving southwards, Mr Maliki requested US air strikes. However, US President Barack Obama said further military assistance was dependent on an inclusive government being formed.
He nevertheless launched air strikes in August 2014 when thousands of members of the Yazidi religious minority became trapped on Mount Sinjar.
In September 2014, Mr Maliki stepped aside and a new Iraqi government was named. The next phase of US assistance will reportedly involve an intensified effort to train, advise and equip the Iraqi military, Kurdish Peshmerga fighters and Sunni tribesmen willing to turn against IS.
It is not clear how new Prime Minister Haider al-Abadi will deal with the Shia militiamen who have stopped IS reaching Baghdad. Some have been accused of operating outside of the state’s control and carrying out reprisal attacks against Sunnis.
At the end of August 2014, Mr Abadi vowed to rebuild the Iraqi army and to create a new “national guard organisation” modelled on the Sunni Sahwa (Awakening) councils that battled al-Qaeda alongside US troops.