Syria has been engulfed in a devastating civil war since 2011 after Syrian President Bashar Assad lost control over large parts of the country to multiple revolutionary groups. The conflict has since drawn in foreign powers and brought misery and death to Syrians.

Syria's army, officially known as the Syrian Arab Army (SAA), is loyal to Syrian President Bashar al-Assad and is fighting to restore the president's rule over the entire country. The SAA has been fighting alongside a number of pro-Assad militias such as the National Defense Force and has cooperated with military advisors from Russia and Iran, which back Assad.

Turkey, which is also part of the US-led coalition against IS, has actively supported rebels opposed to Assad. It has a tense relationship with its American allies over US cooperation with Kurdish fighters, who Ankara says are linked to the Kurdistan Workers' Party (PKK) fighting in Turkey. Turkey has launched multiple military offensives targeting Kurdish militias.

The Kremlin has proven to be a powerful friend to Assad. Russian air power and ground troops officially joined the fight in September 2015 after years of supplying the Syrian army. Moscow has come under fire from the international community for the high number of civilian casualties during its airstrikes. However, Russia's intervention turned the tide in war in favor of Assad.

A US-led coalition of more than 50 countries, including Germany, began targeting IS and other terrorist targets with airstrikes in late 2014. The anti-IS coalition has dealt major setbacks to the militant group. The US has more than a thousand special forces in the country backing the Syrian Democratic Forces.

The Free Syrian Army grew out of protests against the Assad regime that eventually turned violent. Along with other non-jihadist rebel groups, it seeks the ouster of President Assad and democratic elections. After suffering a number of defeats, many of its members defected to hardline militant groups. It garnered some support from the US and Turkey, but its strength has been greatly diminished.

Fighting between Syrian Kurds and Islamists has become its own conflict. The US-led coalition against the "Islamic State" has backed the Syrian Democratic Forces, an alliance of Kurdish and Arab militias. The Kurdish YPG militia is the main component of the SDF. The Kurds have had a tacit understanding with Assad.

"Islamic State" (IS) took advantage of regional chaos to capture vast swathes of territory in Iraq and Syria in 2014. Seeking to establish its own "caliphate," IS has become infamous for its fundamentalist brand of Islam and its mass atrocities. IS is on the brink of defeat after the US and Russia led separate military campaigns against the militant group.

IS is not the only terrorist group that has ravaged Syria. A number of jihadist militant groups are fighting in the conflict, warring against various rebel factions and the Assad regime. One of the main jihadist factions is Hay'at Tahrir al-Sham, which controls most of Idlib province and has ties with al-Qaeda.

Iran has supported Syria, its only Arab ally, for decades. Eager to maintain its ally, Tehran has provided Damascus with strategic assistance, military training and ground troops when the conflict emerged in 2011. The Iran-backed Lebanese Shiite militant group Hezbollah also supports the Assad regime, fighting alongside Iranian forces and paramilitary groups in the country.

In late 2014, with the war in Syria approaching its fourth year and Islamic State making gains in the north of the country, the exodus of Syrians intensified. At the same time, others were fleeing violence and poverty in countries such as Iraq, Afghanistan, Eritrea, Somalia, Niger and Kosovo.

Vast numbers of Syrian refugees had been gathering in border-town camps in neighboring Turkey, Lebanon and Jordan since 2011. By 2015, with the camps full to bursting and residents often unable to find work or educate their children, more and more people decided to seek asylum further afield.

In 2015 an estimated 1.5 million people made their way on foot from Greece towards western Europe via the "Balkan route". The Schengen Agreement, which allows passport-free travel within much of the EU, was called into question as refugees headed towards the wealthier European nations.

Tens of thousands of refugees were also attempting the perilous journey across the Mediterranean on overcrowded boats. In April 2015, 800 people of various nationalities drowned when a boat traveling from Libya capsized off the Italian coast. This was to be just one of many similar tragedies - by the end of the year, nearly 4,000 refugees were reported to have died attempting the crossing.

Countries along the EU's external border struggled to cope with the sheer number of arrivals. Fences were erected in Hungary, Slovenia, Macedonia and Austria. Asylum laws were tightened and several Schengen area countries introduced temporary border controls.

Critics of German Chancellor Angela Merkel's "open-door" refugee policy claimed it had made the situation worse by encouraging more people to embark on the dangerous journey to Europe. By September 2016, Germany had also introduced temporary checks on its border with Austria.

In early 2016, the EU and Turkey signed an agreement under which refugees arriving in Greece could be sent back to Turkey. The deal has been criticized by human rights groups and came under new strain following a vote by the European Parliament in November to freeze talks on Turkey's potential accession to the EU.

With anti-immigration sentiment in Europe growing, governments are still struggling to reach a consensus on how to handle the continuing refugee crisis. Attempts to introduce quotas for the distribution of refugees among EU member states have largely failed. Conflicts in the Middle East and elsewhere show no signs coming to an end, and the death toll from refugee sea crossings is on the rise.