- Decades of discrimination -

Concentrated in northern Syria, Kurds make up around 15 percent of the country's population.

Most are Sunni Muslims, though there are some non-Muslim minorities and many Kurds consider themselves secular.

After a controversial census in 1962, they were stripped of their nationality and have since suffered decades of marginalisation and oppression by Syria's ruling Baath party.

- Neutrality, then autonomy -

When Syria's conflict erupted in 2011, the Kurdish population generally sought to adopt a position of neutrality.

Syria's President Bashar al-Assad made conciliatory gestures towards the Kurds from the earliest days of the conflict, granting citizenship to 300,000 after half a century of waiting.

In 2012, government forces withdrew from Kurdish-majority areas in Syria's north and east, paving the way for Kurds to consolidate control on the ground.

They have since established self-rule in many of these areas, and have sought to prevent rebels and regime from entering them.

- 'Federal region' -

In 2013, the Democratic Union Party (PYD), the political branch of the powerful People's Protection Units (YPG), announced the formation of an autonomous administration after making key territorial gains against the Islamic State (IS) group.

And in 2016, Kurdish authorities announced the creation of a "federal region" made up of those semi-autonomous regions.

It would include three cantons: Afrin (in Aleppo province) Jazira (Hasakeh province) and Euphrates (includes parts of Aleppo and Raqa provinces).

The initiative looked like de facto autonomy, provoking hostility from Syria's mainstream opposition forces and neighbouring Turkey.

At the end of 2016, the Kurds gave themselves a "social contract" -- a Constitution for the "federal region".

In 2017, inhabitants of these regions voted in "communal" elections to elect town councillors.

- Anti-jihadists -

Kurdish fighters have proved to be the most effective anti-IS force in Syria and Washington's best ally in the fight against jihadists.

At the start of 2015, Kurdish forces supported by US-led coalition strikes ousted IS from Kobane on the Turkish border after more than four months of fighting.

In 2016, the Syrian Democratic Forces (SDF), an alliance of Kurdish fighters and Arabs, captured the city of Manbij from IS.

And, in 2017, they overran IS's de facto Syrian capital, Raqa.

- Turkish ire -

At the start of 2018 the coalition announced it was working to create a 30,000-strong border security force in northern Syria, around half of whom would be retrained fighters from the SDF.

The alliance would be made up of Kurdish and Arab fighters.

But Ankara accuses the YPG of being the Syrian offshoot of the outlawed Kurdistan Workers' Party (PKK), which has waged a three-decade rebellion in Turkey's southeast.

On January 20, Turkey launched a new air and ground operation against the YPG-held enclave of Afrin, in northern Syria.