Here is a recap of key events that have impacted the Kurds in Syria, who live mostly in the north of the country and represent 15 percent of the population, according to estimates.

- Protests -

On April 1, 2011 several hundred people protest peacefully in northeastern Syria, the first time Kurds take to the streets since the pro-reform protests erupted in mid-March.

They call for the right to citizenship and "freedom as well", according to witness accounts.

In 1962, 20 percent of Kurds in Syria lost their citizenship following a controversial census. The issue has long poisoned relations between the government and Syria's Kurds.

- Naturalisation -

On April 7, 2011 Syria's President Bashar al-Assad issues "a decree granting Arab Syrian citizenship to people registered as foreigners in the (governorate of Hasakeh)," the SANA state news agency reports.

The decree concerns about 300,000 Kurds.

The next day protests take place in several areas in northern Syria in support of the abolition of the emergency law and the release of prisoners.

Several more demonstrations in the north involving thousands of people take place in the months that follow.

- Assassination -

On October 7, 2011 the prominent Kurdish opposition figure Meshaal Tamo is killed by four masked gunmen in the northeastern city of Qamishli.

Tamo was a member of the newly formed Syrian National Council opposition grouping. Shortly before his assassination he had been released after three and a half years in prison.

The day after Tamo's killing, security forces open fire on a large crowd that had gathered for his funeral.

- Army retreat -

In June 2012 the Free Syrian Army, after the defection of some of its Syrian soldiers, calls on the Kurds to join the uprising.

But the Kurds, wary of the opposition they believe unlikely to recognise their specific case, try to protect their regions from the violence.

In July the army retreats from fighting in some Kurdish regions where fighters close to the outlawed Kurdistan Workers' Party (PKK) are deployed, provoking suspicions of collusion with the regime.

Turkey accuses Damascus of confiding several areas in northern Syria to the Democratic Union Party (PYD), the political branch of the powerful People's Protection Units (YPG).

- Semi-autonomous region -

On November 12, 2013 the PYD and other Kurdish groups announce the establishment of a semi-autonomous region, divided into three zones.

The announcement comes after victories on the ground by Kurdish fighters against rebels and jihadists.

- US ally -

In September 2014 a US-led coalition launches its first raids against the Islamic State group (IS), after the jihadists earlier in the year capture large swathes of northern and eastern Syria.

In October the US State Department reveals that American officials met for the first time Kurds from the PYD, as part of Washington's strategy against IS.

At the start of 2015 Kurdish forces supported by coalition strikes oust IS from Kobane on the Turkish border.

In June the YPG takes control of Tal Abyad, also on the border with Turkey.

The Syrian Democratic Forces (SDF), an alliance of 25,000 Kurdish fighters and 5,000 Arabs -- all Syrian -- is created in October 2015.

Dominated by the Kurdish YPG, the alliance receives aid from the US, in the form of arms and air support for their operations.

Since then the SDF has overrun IS' de facto Syrian capital, Raqa, and a large part of Deir Ezzor province.

- Call for regime help -

On December 28, 2018 the YPG call on Syrian government troops to deploy alongside their own forces in the north to help counter a threatened Turkish offensive.

The call comes days after Washington's surprise announcement it would be pulling its troops out of the country.

The Syrian army is deployed around Manbij, a key city about 30 kilometres (19 miles) south of the Turkish border.