It's time to revisit the topic of a potential civil war in Turkey. In my Aug. 13 column, "Speculation about Turkish civil war is just that," I concluded that because we had not yet seen large-scale operations supported by brigade-sized armored units and air forces, it was too early to discuss the likelihood of civil war.

But since Aug. 13, escalating clashes between Ankara and the Kurdistan Workers Party (PKK) have shifted to urban centers. There are certain thresholds of violence that could provide answers to the question, "Are we heading to civil war?"

For Ankara the signal could be its use of armored forces in cities — firing tank guns at PKK targets and bombing targets in cities and their fringes.

For the PKK, the sure signs of approaching combat would be if it deployed experienced mountain fighters with young and inexperienced Patriotic Revolutionary Youth Movement (YDG-H) militants in towns, forming hybrid units of mountain fighters and urban militants. Another sign would be if the PKK transforms the trenches it has dug in cities into reinforced strongholds — devising armored ambush locations and strengthening these defenses with improvised explosive devices.