By the grisly standards of war-torn Iraq, fighting yesterday in the mountains in the northern part of the country was a mild affair. Iranian artillery shelled villages in the Qandil mountains that are home to various Kurdish militant groups, one of which — the Party for a Free Life in Kurdistan (PEJAK) — is waging a guerilla insurgency against the Iranian government. Though hundreds of villagers fled their homes and two women were wounded, such cross-border violence is becoming a regular feature of life in the north. But yesterday's attack could also be a prelude to a larger struggle.Iraqi Kurdish media are reporting that the Iranian military is massing at the main border crossing into northern Iraq, possibly for an incursion against PEJAK. Clashes between PEJAK and the Iranians have been increasing steadily, and Iraqi Kurdish officials say that about 40 Iranian soldiers were killed on Saturday.Whether or not the Iranians attack, the timing of the buildup is ominous. Last week, the United States announced that it may list Iran's Revolutionary Guard — a branch of the country's military — as a terrorist organization for supplying explosives to Shi'ite militias in Iraq for use against American soldiers. The statement was part of a growing White House campaign aimed at either intimidating the Iranian regime, or at building a case for an American strike against Iran. In that light, yesterday's shelling is a reminder that Iran has the ability to confront the U.S. not just on the streets of Baghdad but also in the one part Iraq so safe that there are hardly any American soldiers: Iraqi Kurdistan.But Iraq's Kurdish region — the country's only success story — is looking increasingly beleaguered. Besides the Iranian army, the Turkish army is also massed at their border with northern Iraq, threatening an invasion if Iraq's Kurds don't do something about another Kurdish radical group, the PKK, which is fighting its own insurgency against the Turkish state. The ruling Kurdish parties of northern Iraq say there is little they can do about these radical groups. Not only are the PKK and PEJAK hardened guerilla fighters in formidable terrain, but the Iraqi Kurds' own security forces are stretched pretty thin keeping their territory safe from Arab terrorists in the rest of the country. That threat is as real as ever. The official death toll from last week's suicide attacks against several towns near Iraqi Kurdistan has risen to over 400 and continues to climb.Iraq's Kurdish leaders have long been trying to steer a course between their patrons in Washington and their powerful neighbors in Tehran. Though they have America to thank for freeing them from the genocidal grip of Saddam's regime, many Iraqi Kurdish political parties took refuge in Iran during those grim years. This spring, Kurds protested vigorously when American soldiers captured several Iranian agents posing as diplomats in the Kurdish regional capital of Arbil. An Iranian incursion into Iraqi Kurdistan would be a poor way of saying thanks.But these days Iraq's Kurds aren't feeling the love from anyone. Last week, America's ambassador to Iraq Ryan Crocker said he didn't think that it would be possible to hold a referendum on the status of Kirkuk this year. Iraqi Kurds consider the oil-rich city of Kirkuk — which is currently under control of the central government of Baghdad — to be the "Jerusalem" of Kurdistan, stolen from them by a Ba'athist ethnic-cleansing campaign in the 1980s. The Kurds have made the return of Kirkuk a central precondition to their participation in a federal Iraq, and will regard any delay as a betrayal. But then again, they are used to betrayal. As the saying goes, the Kurds — a small ethnic group living in the shadows of great empires — have never had any true friends but the mountains.