The Kurds’ most important resource is oil. Erbil, the region’s capital, is an oil boomtown. And after the Iraqi military fled Kirkuk during the Islamic State’s offensive in 2014, the Kurds were able to seize full control of that city and its major oil fields, too. Independence would mean the Iraqi government losing any share of those lucrative resources — an outcome Baghdad has said it is willing to go to war to prevent.
The détente between Iraq and the Kurds has only been a relatively recent development, and has never been strong, even though they are on the same side of the fight against the Islamic State. In the 1970s, Iraqi leaders sent Kurds to concentration camps and razed their villages. In the 1980s, when they sided with Iran in its war with Iraq, President Saddam Hussein killed more than 100,000 of them and attacked the city of Halabja with poison gas.
A no-fly zone, imposed by the United States after the 1991 gulf war and a failed Kurdish uprising, protected the Kurds for years in northern Iraq. And after the United States-led invasion of Iraq in 2003, the Kurds and the Iraqi government essentially had to get along, under pressure from American officials. But after the Kurdish referendum vote, Iraq has halted flights at the international airports and threatened to send troops to retake the Kirkuk oil fields and disputed areas.
Credit Umit Bektas/Reuters
Fear of a domino effect in Turkey.
The Turkish government has long looked at any potential Kurdish state on its borders as an existential threat, possibly encouraging the millions of Kurds who live in southern Turkey — who have long been repressed by the government both culturally and militarily — to stage a breakaway of their own.
Those fears have been forged by years of violent conflict with Kurdish militants within Turkey that has led to a death toll of 40,000 and rising. The militants — the Kurdistan Workers’ Party, better known as the P.K.K. — are officially considered terrorists by Turkey, the United States and the European Union. The government in Iraqi Kurdistan has also publicly rejected them, but from time to time, the Turkish government has made military strikes into Kurdistan, saying that P.K.K. fighters were sheltering there.
Now, the Iraqi Kurds’ move to support independence has led to concern that Turkey might go as far as invading to stop the process.
Credit Mauricio Lima for The New York Times
Complex alliances in Syria.
Syria’s civil war, and the global fight against the Islamic State there, has provided an opportunity for the country’s Kurdish population — estimated at around 300,000 before the war — to find some autonomy in northeastern Syria, near the Turkish and Iraqi borders. Kurdish fighters there were for years the United States’ ally of choice in fighting the Islamic State.
But those same Kurdish fighters in Syria are also generally loyal to P.K.K. leadership, even though they take pains to use a different name. Their rise as a combatant force has alarmed Turkey, which has demanded that the United States stop supporting them and start shelling places in their territory.
In general, the Kurds in Syria have tried to stay roughly neutral when it comes to the government of President Bashar al-Assad. And Syrian forces, consumed with major cities in the heartland, have mostly left them alone. But now that the balance of power has shifted in Syria, with interventions from Russia and Iran helping Mr. Assad defeat the network of insurgencies against him, there is a renewed possibility that the government will not look kindly on an armed and autonomous Kurdish region within its national borders.
Credit Rodi Said/Reuters
Friends and enemies in the United States.
Washington has relied on Kurdish help in the Middle East for decades, but has never officially backed plans for an independent Kurdish state.
That is because the United States is also heavily dependent on its alliances with Turkey and Iraq, two nations crucial to regional stability and to the coalition to defeat the Islamic State, but which have both sworn to prevent Kurdish independence.
The White House this week called the independence referendum in Iraq “provocative and destabilizing.” Brett H. McGurk, the United States special envoy to counter the Islamic State, described it as “a very risky process” with “no prospect for international legitimacy.”