The latest string of victories by Islamic militants in Iraq raises an enormous and obvious question: What’s the U.S. doing to help the Kurds?

This week, fighters from Islamic State in Iraq and al-Sham, or ISIS, captured the town of Sinjar and, the next day, Mosul Dam, the biggest dam on the Tigris River. These victories offer two terrifying prospects, one for humanitarian reasons, the other for strategic reasons.

Sinjar is home to several thousand members of the Yazidi sect, a religious minority with roots in Islam and Zoroastrianism. Islamist extremists, including those who make up the vanguard of ISIS, regard Yazidis as apostates. There is every reason to fear the worst about what the fighters in ISIS will do to the Yazidis. In other towns that ISIS has captured, militants have crucified and beheaded their enemies. Some two hundred thousand people are fleeing Sinjar and Tal Afar, a nearby town. A senior official with the United Nations, which is normally quite restrained in its public pronouncements, said, on Sunday, that “a humanitarian tragedy is unfolding in Sinjar.”

It gets worse. According to Iraqi state television, ISIS militants captured Mosul Dam, which regulates the water flow to Mosul, the country’s second-largest city, and to a string of towns and cities to the south. A hydroelectric plant at the dam provides electricity for much of the same area. If ISIS’s leaders decide to, they could flood cities, towns, and fields along the Tigris as far south as Karbala, south of Baghdad. The men who run ISIS have already demonstrated their capacity for far-out nihilism, so we don’t need to wonder whether they’re capable of deciding to do something like this.

What can be done? For starters, the U.S. can help the one group that is trying hardest to resist ISIS: the Kurds. The Kurds, who occupy a large swath of northeastern Iraq, now stand face to face with ISIS across a six-hundred-mile frontier. The Kurds are among America’s best friends in the Middle East; they are pro-Western, largely secular, and largely democratic. Since 1991, when Saddam Hussein’s latest attempt to launch a genocidal campaign against them was thwarted by the United States, the Kurds have more or less governed themselves. During the American war, from 2003 to 2011, not a single American soldier was killed in the Kurdish region. The Kurds regard themselves as culturally and linguistically apart from the Arabs—Sunni and Shia—who inhabit the rest of Iraq. These days, fewer and fewer Kurds even know how to speak Arabic.

And that’s the problem, at least according to the United States. Since 2003, American policy toward Kurdistan has been “one Iraq.” That is, no matter how friendly the Kurds are, no matter how pro-Western, American policy has been to keep Iraq together. That means: don’t do anything that helps the Kurds too much, lest they break away from Iraq and declare independence, which is most what most Kurds want.

Until recently, this made a certain amount of sense, even if it denied the Kurds their true desires. But, since June, when ISIS militants swept across the Syrian border and captured huge portions of northern and western Iraq, that policy has been more and more difficult to justify. The Kurds now share a huge border with ISIS-controlled territory, and only a few miles of what is left of Iraq. The Kurdish militia, called the peshmerga, fights ISIS every day. Since early this year, the Kurdish regional government, which presides over the area, has been cut off entirely from Iraq’s oil revenue—to which it is entitled by law—by the government in Baghdad. The way that Prime Minister Nuri al-Maliki is dealing with the Kurds is the same way he dealt with the Sunni Arabs—harshly and arbitrarily. Indeed, Maliki’s actions toward the Sunnis precipitated the events that led to the ISIS takeover.

In spite of all this, the Obama Administration seems bent on squeezing the Kurds to remain part of Iraq. According to Reuters, when the Kurds recently asked for military assistance the White House told them to work with the government in Baghdad, which, as the White House well knows, is tantamount to refusing them outright. And American officials have made it difficult for the Kurds to sell their own oil, stating publicly that any company which buys oil exported unilaterally by the Kurds risks incurring legal problems. Oil, for all practical purpose, is the Kurds’ only export, a case that Kurdish officials made again this week.

The militants in ISIS have swept across much of northern and western Iraq, and there is no sign that they have any intention of slowing down. In a surprising—and encouraging—turn, Maliki has apparently ordered the Iraqi Air Force to carry out air strikes to help the Kurds. That said, the Iraqi Army has proved itself utterly ineffectual in combating ISIS. If the U.S. decided to help the Kurds, there would be no guarantee that the Kurds wouldn’t later use those weapons to further their own interests.

But what other choice is there? If anyone is likely to slow down ISIS, it’s going to be the Kurds—regardless of whatever they’re planning to do later on.