Hostage-taking, massacres, bombs in Turkish tourist resorts and attacks on Turkish consulates in Europe are part of a strategy to inspire fear and win an international profile for an organisation that even other Kurdish guerrilla groups are not quite comfortable with.
Turkey tries to dismiss the PKK as terrorist bandits, but that does not explain the success of this part- Marxist, part-nationalist, part-Islamic group, where it finds its financial support and who its foreign backers are. It appears to have been given at least transit facilities by hardline elements in Iran, an allegation denied by Iranian officials.
President Saddam Hussein of Iraq has given some aid to the PKK. But the PKK also maintains offices in northern Iraq, which is an anti- Saddam area controlled by Kurdish guerrillas, even though a Turkish- Iraqi Kurdish guerrilla offensive in October forced the PKK away from bases on the Iraqi-Turkish border.
The PKK's main backer has always been Syria. The PKK leader, Abdullah Ocalan, has been based in Damascus or the Syrian-controlled Bekaa Valley for more than a decade. Some speak of a weakening of Mr Ocalan's influence due to health and other problems, but the increasingly powerful chief of the PKK's military wing, Cemil Bayik, is also close to Syrian control.
But the key to Turkey's Kurdish problem is in Turkey itself. In the past nine years the insurgency has left 6,900 people dead, 1,015 of whom have died since May, when the collapse of a unilateral guerrilla truce plunged the south-east into its worst bout of bloodshed yet.
The rebels are a powerful and feared symbol of a national struggle for many of Turkey's 12 million Kurds.
They have filled a vacuum cleared for them by the Turkish security forces, who have refused to allow the emergence of a moderate Kurdish nationalist political centre.