The Kurds are one of the indigenous people of the Mesopotamian plains and the highlands, areas that today are contained within southeastern Turkey, northeastern Syria, northern Iraq, northwestern Iran and southwestern Armenia.
Estimated at between 25 million and 35 million people, the Kurds are the fourth-largest ethnic group in the Middle East.
Here's a brief look at their political history in the four countries where they largely live:
Iraq
Iraqi Kurds, estimated to make up 15 to 20 percent of Iraq's population of 38 million people, populate a mountainous region in northern Iraq and enjoy more national rights than Kurds in the neighboring three countries.
The Iraqi Kurds have gained substantial political recognition since the fall of Saddam Hussein's regime in 2003.
In 2005, the Iraq constitution accepted Kurdish as an official language, along with Arabic, and recognized the predominantly Kurdish provinces of Irbil, Sulaymaniyah and Duhok as a federal entity known as the Kurdistan Region, which has its own military, known as the peshmerga.
The relationship between the Kurds and the Iraqi government, however, has a history of bloody confrontations and often brutal crackdowns by the central government, particularly during Hussein's reign.
Feeling pressured by the Kurdish resistance movement, Hussein's forces in late 1980s unleashed the Anfal campaign, which reportedly left 180,000 Kurds killed or missing, and about 4,500 villages destroyed. The Iraqi government campaign also used chemical weapons, particularly in the 1998 gas attack on the town of Halabja, which left nearly 5,000 residents dead.
Rights organizations, such as Human Rights Watch, said the Anfal campaign was a systematic ethnic-cleansing program that amounted to genocide. Norway, Sweden, the United Kingdom and South Korea officially recognize the campaign as genocide.
In March 1991, after their uprising was crushed by the Iraq government, about 1.5 million Iraqi Kurds fled into Iran and Turkey, leading to a refugee crisis. In response, an anti-Hussein international coalition established a partial no-fly zone in northern Iraq to allow the return of refugees and protect them from a future aggression. For years afterward, the zone allowed the Kurds to establish their regional government and parliament.
WATCH: Facts about the Kurds
The rise of the Islamic State (IS) terror group in 2014 weakened the Iraqi government. The Kurdish peshmerga moved into areas from which Iraqi forces retreated as IS took control.
The Kurds announced they had no intention of withdrawing from these areas, which the Iraqi constitution labels as disputed territories between the Kurdistan Region and the Central Government, and requires a referendum vote on their status.
As IS started losing territory, and the Kurdish peshmergas gained international support for their role in defeating the militants, the Kurdistan Region said it intended to hold a referendum for independence. The vote in September 2017 received 93.25% support, but it was later crushed in an Iraqi government operation, allegedly backed by Iran. It was the most recent attempt by Kurds to establish a state of their own.
Syria
In Syria, Kurds make up nearly 15 percent of Syria's 22 million prewar population. They primarily live in north and northeastern parts of Syria, with significant Kurdish communities in major Syrian cities, such as Damascus and Aleppo.
Since the establishment of a modern state in Syria in the 1920s, Syrian Kurds have been deprived of political and linguistic rights.
The first Kurdish political party in Syria was founded in 1957, influenced by Iraqi Kurds. The Kurdistan Democratic Party of Syria called for political and cultural rights for the Kurdish minority in the Arab-majority country, but its leading members were faced with imprisonment and persecution.
With the eruption of Syria's civil war in 2011, Syrian Kurds were able to be in charge of their regions for the first time.
The People's Protection Units (YPG) took control of the area after Syrian government troops withdrew to focus on fighting rebel groups elsewhere in the war-ravaged country.
With the rise of IS in Syria, the YPG proved to be an effective force in the fight against IS. Consequently, the U.S.-led coalition provided assistance to the Kurdish group to remove IS from other territories in Syria.
In 2015, the Syrian Democratic Forces (SDF) was established to include non-Kurdish fighters as well.
With U.S. support, the SDF captured most areas from IS control, including Raqqa, the capital of its so-called caliphate. In March 2019, the SDF declared the territorial defeat of IS after pushing out the terror group from its last pocket of control in eastern Syria.
The Kurdish-led SDF now controls nearly one-third of Syria's territory, which has effectively become a semiautonomous region.
But Turkey considers the YPG an extension of the Turkish-based Kurdistan Workers' Party (PKK), a group designated as terrorists by Turkey, the European Union and United States.
This month, U.S. President Donald Trump announced American forces would withdraw from northeast Syria, allowing the Turkish military to launch its long-planned offensive against Syrian Kurdish fighters.
Days after the U.S. announcement, Turkey began its operation on two Kurdish-held cities along the Syria-Turkey border. Rights groups, including Amnesty International, said the Turkish-led campaign has killed hundreds of civilians and displaced thousands of others.
Despite a cease-fire that was brokered by the U.S. last week and Turkey's assurances that it would not resume its military offensive, fighting could resume as both Kurdish forces have not agreed to all the terms of the deal.
Turkey
The Kurds are the largest non-Turkish ethnic group in Turkey. They constitute up to 20 percent of Turkey's population.
For decades, the Kurds were subjected to the so-called "Turkification policies" of the state, and their ethnic identity was denied. Their language was restricted, and naming their children in Kurdish was banned. For decades, they were referred to as "mountain Turks."
The question of an independent Kurdistan has a long history that dates back to the Ottoman Empire. In the Treaty of Sevres in 1920, the Western allies promised an autonomous Kurdistan. However, that was never fulfilled because the Republic of Turkey was founded in 1923 following the Treaty of Lausanne.
As a unitary nation state, Turkey considered the Kurds a threat to its national unity and pushed back on demands for equal citizenship rights.
PKK
In 1978, Abdullah Ocalan founded the Kurdistan Workers' Party (PKK) with the aim of establishing a united, independent Kurdistan within Turkey, but also including parts of Iraq, Iran and Syria. The group started its armed insurgency inside Turkey in 1984, and since then, tens of thousands of people have been killed and hundreds of thousands displaced as a result of the conflict between the Turkish government and PKK.
In 1999, Ocalan was arrested in Kenya by Turkish intelligence forces. He is serving a life sentence at an island prison near Istanbul.
In March 2013, during the Kurdish "Nowruz," or new year, celebrations, Ocalan sent a letter to supporters. He called for a cease-fire, as well as setps to disarm and withdraw from Turkey, and an end to armed struggle. The Turkish government praised the letter.
In July 2015, a two-and-a-half-year cease-fire broke down, and the conflict resumed.
According to International Crisis Group, more than 4,500 people have been killed in clashes or terror attacks since 2015.
Iran
Ethnic Kurds make up nearly 9% of Iran's 80 million population. They are largely Sunni Muslims, but there are some Shiite and Zoroastrian Kurds as well.
The Kurdish political movement in Iran started with the establishment of the Kurdistan Democratic Party in 1946. Under the leadership of Qazi Mohammad, the group declared a Kurdish republic in the city of Mahabad that same year. Nearly 11 months later, however, Iranian government forces entered Mahabad to crush the new Kurdish entity. Mohammad was executed immediately.
In 1979, after the Islamic revolution toppled the last shah of Iran, Mohammad Reza Pahlavi, the new Islamist government carried on the subjugation of the Kurds. The powerful Islamic Revolutionary Guard Corps (IRGC) began targeting Kurdish activists at home and abroad.
In 1989, Abdul Rahman Ghassemlou, an influential Iranian Kurdish leader, was assassinated in Vienna, Austria. The operation was reportedly carried out by the IRGC.
Influenced by the Turkish-based PKK, the Kurdistan Free Life Party (PJAK) was founded 2003 in Iran. Ever since, the group has been engaged in occasional clashes with Iranian security forces.
