Now that the Turkish legislature has approved attacks on PKK rebels in Iraq, how serious is the risk that the Turkish military will actually carry out these assaults? Very serious.
Turkish politicians no longer believe that the Iraqi government is capable of dealing with the PKK. In fact, it's hard to believe that the Iraqi military would make the PKK a high-priority target, given how occupied the Iraqi Security Forces (ISF) are with other problems. While Turkish troops crossing the border into Iraq might be embarrassing, Iraqi leaders know that it's hardly a nightmare scenario.
The political and diplomatic backlash from Turkish cross-border operations all depend on what form these attacks take. Options range from the plausible, such as occasional raids against suspected PKK concentrations, to the unbelievable, such as a de facto occupation of northern Iraq. While some Turks might like to see the PKK crushed once and for all, the general staff of the Turkish Armed Forces knows that the real objective is to drive the PKK away from the border, making it increasingly harder for PKK fighters to operate inside Turkish terrority. Turkish forces might easily accomplish this objective without a massive military intervention in Iraq.
This strategy might run aground if the PKK continues to elude the Turkish military. The strategy might really jump off the rails if Iraqi civilians are killed during these operations.
Fortunately, there are other interested parties that can lower the risk of these sorts of mishaps: other Iraqi Kurds. The PKK is hardly popular among other Kurds, who don't want their political fortunes to be hostage to the Kurdish version of the PFLP. Frictions between the PKK and rival groups, such as the Patriotic Union of Kurdistan (PUK) and the Kurdistan Democratic Party (KDP), existed long before the 2003 invasion of Iraq. (For a recent example of how intansigent the PKK can be, click here.) While Kurdish leaders such as Iraqi president Jalal Talabani can't overtly cooperate with the Turks, they can moderate the political backlash from any Turkish incursions. While no one is likely to say it to a reporter, other Kurds might also provide information about the PKK to Iraqi, American, and even Turkish authorities.
For now, we'll have to wait and see what happens. However, the more Iraq creeps towards a Hobbesian state of nature, the fewer reasons the Turkish government has to respect the border with Iraq.