Since Islamic State militants swept through Iraq and Syria last year, one group has found itself on the front lines of the ongoing war: the Kurds.
The Kurds' involvement in the conflict is difficult to understand because of their own troubled history that spreads across several regional borders.
Here is a look at the current Kurdish crisis and how it came to be:
Who are the Kurds?
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. They form a distinctive community, united through race, culture and language, and while most of them are Sunni Muslims, they also adhere to a number of different religions and creeds.
They are considered the largest ethnic group in the world to be stateless.
Why don't they have a country?
After World War I and the defeat of the Ottoman Empire, the victorious Western allies made provision in the 1920 Treaty of Sevres for the formation of a Kurdish state, to be known as Kurdistan.
But their hopes were dashed three years later when the Treaty of Lausanne, which set the boundaries of modern Turkey, made no provision for a Kurdish state and left Kurds with minority status in their respective countries. Over the next 80 years, any move by Kurds to set up an independent state was brutally quashed.
The current war against IS presents a huge opportunity for the Kurds to project legitimacy on the international stage.
What is their role in the war against the Islamic State?
The Kurds were pulled into the war against IS when the terrorist group turned its attention on three Kurdish enclaves that bordered its territory in northern Syria in 2013.
That was followed by Islamic State's large-scale offensive through northern Iraq in 2014, which led to neighboring Kurdish militant groups uniting in a coordinated battle.
The government of Iraq's semiautonomous Kurdistan Region sent its Peshmerga forces to areas abandoned by the army.
But the IS jihadists pushed back the Peshmerga, allowing several towns inhabited by religious minorities to fall — notably Sinjar, where thousands of Yazidis where sheltering.
Alarmed by the Peshmerga's defeat and the potential massacre of the Yazidis, the U.S. launched airstrikes in northern Iraq, and European countries began sending arms to the Peshmerga.
While the Peshmerga have made some gains in Iraq, they continue to face grave challenges against the IS militants in Syria.
Kurds vs. Turks vs. IS
The Islamic State battles in Syria have begun to directly affect Turkey. The militants' push on the enclave around the northern Syrian town of Kobani forced more than 160,000 people to flee into Turkey. Despite that, Ankara refused to attack IS positions near the border or allow Kurds to cross to defend it, triggering Kurdish protests and a threat from the Turkish Kurdistan Workers' Party (PKK) to pull out of its peace talks with the government.
Turkey's cease-fire with the PKK finally collapsed in July. Since then, Turkish warplanes have been carrying out frequent bombing raids on PKK camps in mountainous northern Iraq and in Turkey's mainly Kurdish southeast. The rebels have responded with a string of bloody attacks on security forces.
Ankara fears that Turkish Kurds will cross into Syria to join the PYD — an offshoot of the PKK — and then use its territory to launch attacks on Turkey.
The Kurds have been engaged in political and territorial warfare in the region for decades. Now with the global fight against IS and the collapse of the borders in Syria and Iraq, the stakes are higher than they have ever been for a redrawn Middle East.
The current battles and the continued economic and political instability in Turkey, Syria, Iraq and Iran will be central in determining the future shape of the region.