As Sunni fighters led by the jihadist group ISIS have pressed forward, capturing the Iraqi cities of Mosul, Tikrit, and Ramadi and encircling Baghdad, Iraq's Kurds have taken advantage of the chaos by expanding their territory and pushing for greater autonomy.

During the past month Sunni militants have spilled out of Syria, dissolved the Iraq-Syria border, and established an Islamic caliphate that straddles the two countries. The Iraqi army fled in the face of the Sunni advance, but Kurdish militia fighters repelled ISIS (Islamic State of Iraq and Syria) at their borders. On June 12, Kurdish militias advanced, seizing oil-rich Kirkuk, a city at the edge of Kurdistan that Kurds claim as their own, but which the Baghdad-based government considers beyond Kurdish borders.

With the Iraqi central government in shambles, Kurdish leaders are now calling on Iraq Prime Minister Nouri al-Maliki to step down.

Sitting atop an ocean of newly conquered oil fields and emboldened by the breakdown of the Iraqi state, Kurdish President Masoud Barzani declared that the Kurds would not cede their newly conquered territory. "We cannot remain hostages for the unknown … The time is here for the Kurdistan people to determine their future," he said.

But the recent turmoil in Iraq does not alone explain the surge toward greater Kurdish independence. Since the founding of modern Iraq nearly a century ago, Kurds in the north—nestled along the Turkish, Syrian, and Iranian borders—have chafed against the central government in Baghdad. (Related: "Iraq Crisis: 'Ancient Hatreds Turning Into Modern Realities.'")

View Images Locals wait in an early morning gas line in Dohuk, Iraq on November 11, 1991. Some people waited as long as 5 days to get fuel. PHOTOGRAPH BY ED KASHI, NATIONAL GEOGRAPHIC

Distinct Traditions

The seeds of the conflict can be found in the unique predicament of the region's estimated 30 million to 35 million Kurds, the world's largest ethno-linguistic group without a state of their own. Kurds are a traditionally nomadic people from the crossroads of Mesopotamia, Anatolia, and Persia, united by a common mother tongue—a group of Iranian languages known as Kurdish—and a shared history of life on the margins of the greater regional empires in western Asia.

Though most Kurds are Sunni Muslims, they have no affinity with the ISIS-led Sunni insurgency, and there are Christian, Jewish, and Shiite Kurdish minorities. As a multi-religious community, they are united by a historical connection to Kurdistan. "The Kurds are one of the oldest ethnic groups in the entire region—and they consider Kurdistan to be their homeland," says Christian Sinclair, president of the Kurdish Studies Association and assistant director of the Center for Middle Eastern Studies at the University of Arizona.

For centuries the rugged terrain of Kurdistan served as a buffer between the Ottoman Empire to the west and its Persian rivals—first the Safavids and later the Qajars—to the east. This particular geographic predicament helps to explain how Kurds retained their own distinct identity. Until the 19th century Kurds were organized into a mosaic of independent chiefdoms in the contested frontier zone. Caught in the middle of a centuries-long imperial rivalry, they maintained a certain degree of self-rule and often were deployed as proxies in wars between the Ottomans and the Persians.