The Big Question: Who are the PKK, and could they draw Turkey into the Iraq conflict?

Where do the PKK come from?

The Kurdistan Workers' Party, established in 1970, is a Marxist-Leninist and nationalist Kurdish guerrilla group that since the mid-1980s has been using violence to push for an independent Kurdish state in south-east Turkey. Some half of Turkey's Kurdish population – 15 per cent of Turkey's total of 73 million – is concentrated in the region. The party is proscribed as a terrorist group in the UK, the US and several other countries. In the past 10 years its demands have moderated to autonomy within Turkey. It suffered a major reverse in 1999 when its leader, Abdullah Ocalan, was captured but in 2004 felt sufficiently strong to resume its campaign of violence. Since the armed struggle began, some 37,000 people have died.

Why is it in the news now?

PKK guerrillas have hideouts in the high, rugged mountains dividing Turkey from northern Iraq, and in the past month they have repeatedly launched attacks on Turkish army patrols, killing dozens of Turkish soldiers. The last incident occurred on Sunday when guerrillas blew up a bridge that a Turkish patrol was crossing, killing eight of them. Several more were killed in a separate explosion. PKK sources published the names of seven of the Turks reported missing, making it clear that the attack was committed by the group.

What happens next?

The Turkish government under Prime Minister Tayyip Erdogan is under increasing pressure to take decisive action against the guerrillas. The Turkish parliament only last week passed a law enabling the army to cross the Iraqi border in pursuit of the PKK after previous incidents. A retired Turkish major general told The New York Times that with the latest incident, "the arrow has left the bow. No room is left for the government to hesitate, postpone or fail to launch a cross-border operation." The nationalist daily Cumhuriyet screamed "Enough is enough," and demonstrators took to the streets across the country demanding tough military action. Windows of the office of the most important Kurdish political party were broken in Istanbul.

So it looks like an invasion, does it?

Conceivably, but with the utmost reluctance on the part of Mr Erdogan. The conservative, pro-Islamic leader of the AKP (Justice and Development Party) who won a strong new mandate at a general election in the summer has worked hard to solve Turkey's long-running Kurdish problem by non-military means. He is also committed to doing all he can to getting Turkey into the European Union. A full-blooded cross-border campaign that satisfied the hard-line Turkish nationalists would undo both of those programmes at a stroke. As one member of the AKP, Suat Kiniklioglu, who also sits on the Foreign Affairs Committee, put it, "We don't want to go into northern Iraq – it's a mess. We are a country negotiating with the European Union."

Would it end the PKK problem?

Most unlikely. The border area is ideal guerrilla terrain, high, rugged, inhospitable mountains. The guerrillas, who have had years to prepare themselves, are split into small cells and scattered across the mountains in hideouts. Far from obtaining a clear-cut victory and the defeat of the PKK, the result of a military campaign is more likely to be that Turkey would be sucked into an Iraqi quagmire of its own. One reason the PKK is again a force to be reckoned with is that the Iraqi insurgency has enabled it to lay hands on huge quantities of arms, thus making it a more formidable force than in the recent past.

Can the Iraqi government stop the guerrillas?

They say they are going to try. Turkey is sceptical. After all, the president of Iraq, Jalal Talabani, is himself a Kurd. The PKK is an irritant to Iraqi Kurdistan's regional government, which has requested the guerrillas to lay down its arms and disperse. But his words leave Mr Erdogan unconvinced. "It is beautiful to say such words," he said. "But we would like to see what its outcome is going to be." As both Talabani and Erdogan well know, the Baghdad government's writ does not run in Iraqi Kurdistan. Even Saddam was unable to extirpate the PKK from the region.

What does the US think about all this?

It is extremely unhappy. Turkey, after all, is a founder member of Nato: a Turkish invasion of northern Iraq would set one Nato member against a country propped up and occupied by another. Iraqi Kurdistan is the one part of Iraq that has enjoyed relative peace and security since the toppling of Saddam, and a full-scale assault could see the one fragile achievement of the US-led invasion undone. So now the US has launched what a Bush spokesman described quaintly as "a diplomatic full court press " to try and stop a Turkish invasion happening. Secretary of State Condoleezza Rice called Mr Erdogan on Sunday and according to Erdogan, underlined "our righteousness ... (and) said, 'allow us a few days'."

So who would gain from a Turkish assault?

Until the latest attack, this was a matter of debate. There are grave differences of philosophy and opinion between Turkey's secular conservatives, heirs to the father of the nation, Mustafa Kemal Ataturk, and the pro-Islamic yet in many ways socially progressive force of the Justice and Development party, which is now unassailably in power in Ankara.

Given the murk in which the army operates, there were analysts who believed that it was the aggressor in the recent clashes, and had initiated them with the aim of embarrassing Erdogan, scuppering or further delaying the effort to join the European Union, and frustrating his policy of drawing the Kurds deeper into the Turkish polity.

This Machiavellian explanation is still not impossible, and the PKK has consistently claimed that it has only killed Turkish soldiers in self-defence. But now, with the PKK admitting clearly its role in the latest attack, the campaign is increasingly seen as a bid by the PKK, to make itself a relevant force again, polarising Kurdish opinion within Turkey and thereby weakening the Kurdish moderates.

How can Turkey's friends help?

EU countries like Britain – by chance, Erdogan arrives for talks with Brown today – are probably asking themselves this very question. The short answer, besides the usual statements condemning the PKK which "is clearly trying to undermine the Turkish government's efforts to improve the lives of people in southeast Turkey", as Gordon Brown's spokesman put it yesterday, is not a great deal. Britain also urged Turkey "to continue to seek a solution through dialogue with the Iraqi government."

Will Turkey invade?

Yes...

* If new serious attacks occur

* If the generals insist there is no alternative

* If Erdogan believes it is the only way to assuage public opinion in Turkey

No...

* If the attacks by the PKK now cease

* If the Kurdish regional government in Iraq can talk the PKK down

* If Erdogan can persuade his countrymen that a military campaign would solve nothing