- Mountain people -

The Kurds inhabit mainly mountainous regions that cover almost half a million square kilometres (200,000 square miles), spanning from southeast Turkey through northern Syria and Iraq to central Iran.

They represent about 20 percent of the overall population in Turkey, around 10 percent in Iran, 15-20 percent in Iraq and 15 percent in Syria.

The Kurds have preserved their culture, dialects and clan-based social structures. Large expatriate communities exist in Armenia, Azerbaijan, Germany and Lebanon.

Although predominantly Sunni Muslims, some are Christians and their political structures are often non-denominational.

- Tense ties with host states -

The collapse of the Ottoman Empire at the end of World War I opened the way to the creation of a Kurdish state, which was provided for in the 1920 Treaty of Sevres.

However, after the victory of Mustafa Kemal (Ataturk) in Turkey, the WWI Allies went back on their decision.

Persisting Kurdish ambitions for a unified nation are seen as a threat to the main host countries.

In Turkey the outlawed Kurdistan Workers' Party (PKK) has been labelled a terrorist organisation by the European Union and United States. More than 30 years of fighting with Turkish forces has killed more than 40,000 people.

Turkey, which carried out two offensives in Syria in 2016 and 2018 to push back Islamic State group and Kurdish fighters from its border, has threatened the Kurds with a new offensive.

In Syria the Kurds have for decades been marginalised and oppressed by the regime. They took a neutral stance vis-a-vis the regime and rebels at the beginning of the country's conflict in 2011, going on to take advantage of the chaos to set up an autonomous region in the north.

In Iraq, Kurds persecuted under dictator Saddam Hussein rose up in 1991 after Iraq's defeat in Kuwait during the Gulf War. They established a de facto autonomy in the north, which was formalised by Iraq's 2005 constitution.

In September 2017 Iraq's Kurds overwhelmingly voted for independence in a non-binding referendum, acting against the advice of Baghdad and the international community. In retaliation the regime snatched back disputed territory.

In Iran, several attacks have been blamed on Kurdish rebels, whose support bases are in Iraq. A Kurdish uprising was harshly repressed following the Islamic Revolution in 1979.

- Anti-IS spearhead -

Kurdish peshmerga fighters are considered to be experienced warriors and Western countries have provided them with air cover, sophisticated weapons and training to combat IS.

In Syria, the US-backed Kurdish People's Protection Units (YPG) are one of the most effective forces against the jihadists.

In October 2017 the YPG-dominated Syrian Democratic Forces (SDF) drove IS from its de facto capital Raqa. They continue to fight the jihadists in their last pockets of resistance in the east.

In Iraq, Kurdish peshmerga fighters also helped push back IS.

- Internal divisions -

The Kurds have never lived under a single, centralised power and are split among a myriad of parties and factions.

While some of these groups straddle borders, others are in conflict with each other because of alliances with the governments where they live.

Iraq's two main Kurdish parties, the Kurdistan Democratic Party (PDK) and Patriotic Union of Kurdistan (PUK), were locked in a 1994-1998 conflict that left 3,000 people dead. They reconciled in 2003.