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China says it is facing a growing threat from militant Islam. It is in the midst of a year-long crackdown on what it describes as terrorism driven by religious extremism. The campaign is focused on the western province of Xinjiang, home to China's Uighur ethnic minority, who are predominantly Muslim.

This is a story about China's wild west, a place where different rules apply.

Our driver and local guide is called Army. Many Chinese born in Chairman Mao's era have names that are martial, patriotic or ideological. I guess Army is as good a name as any other.

We meet in the high altitude air of Kashgar. It's two flights from Beijing, 2,000 miles away, much of it desert and mountain.

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Kashgar is the last of the legendary oasis towns on the Chinese side of the ancient silk road. Closer to Baghdad than to Beijing. Next stop Pakistan.

Our flight is late in because it snowed overnight, the temperature dropping to minus 14C and turning the runway to ice.

But an unforgiving winter is only the most ancient of Kashgar's challenges.

This city is also the front line in a tussle for 10 million Uighur souls. You can start charting the front line even as you leave the airport.

The soldiers in khaki with hi-tech bayonets look straight through us foreigners, through the Han Chinese passengers and through the old Uighur women in shawls and fur coats.

But young Uighur men are stopped and searched.

We load our bags into Army's 4x4 and he passes over headscarves and maps, along with a flatbread the size of a dinner plate because we haven't had time for lunch.

He explains that though everyone here works on Kashgar time, which runs two hours behind the rest of China, we'd better stick with Beijing time so as not to get confused.

Eat your bread seeded side towards you, he advises, or you'll offend local sensibilities.

As we pull out into the traffic, Army explains that he grew up here in the 1960s and 70s.

It was before the troubles between the Han Chinese and Uighur communities. He's a Han but went to school with Uighurs and still has Uighur friends.

Like every community, he shrugs, there are good people and bad people.

Xinjiang Province

•Xinjiang province has a history of autonomy but was brought under Chinese control in the 18th Century

•Russian influence remained strong and the Soviet Union supported an Uighur-led East Turkestan Republic in the north of the region in 1944-1949

•It is a similar size to Iran and has considerable oil reserves

On either side of the road stretches a leached landscape under a leaden sky. The air is too dry for more than a light dusting of snow.

Mudbrick houses, empty fields, a solitary crow on a wire. And cantering along the road straight out of a childhood fairytale, hunched old men with tall hats and wispy beards on donkey carts.

I've been here before. But that was 30 years ago. I was a carefree young teacher straight out of university and it was before the troubles.

I'm nervous about coming back as a reporter. I don't speak Uighur, only Chinese.

I'm afraid of asking questions which might put people in danger. And afraid of not asking them and leaving with as little idea of what's going on as when I arrived.

Army warns that there's a police checkpoint up ahead. Only two days ago, 15 people were killed in a big attack and security is tight as a result.

I'm not going to ask Army what he thinks about Xinjiang's violence. You can go to jail for having your own view here, or even worse, criticising government policy.

Army's phone keeps ringing. It sounds like it might be a girlfriend. I'm just about to mention that the BBC believes in two hands on the steering wheel when the checkpoint appears.

A carful of Uighurs are having their papers checked. We pull in behind and a stony-faced officer motions everyone out of the vehicle.

We file into a concrete bunker with riot shields, batons and helmets lined up against the wall.

A dozen or so police officers ask if we are journalists and where are we going.

The answer to the first question has to be yes but we'd rather not tell them where we're going because that will give us even less chance of getting there. We need a coherent cover story.

Army comes to the rescue, offering a plausible tale about places we want to film.

Plausible enough to get our documents back but not to plausible enough to get us through the checkpoint.

Foreign reporters may not be a terrorist threat but they can be a danger to the official version of events.

As we U-turn and head back in the direction we came, Army mutters that things must be bad to have the local police chief out at a checkpoint on a Sunday afternoon.

Who knows what really happened, he muses. But asking questions gets you nowhere and thinking too hard serves no purpose.

I observe that in our first police encounter, our driver has shown greater competence than anyone else in the team.

Our Han Chinese producer suggests this is because Army used to be a policeman. I wonder why I'm only learning this now. But it figures. Army exudes the authority and calm of a seen-it-all police officer.

Back in town, we're not clear whether it's Beijing time or Xinjiang time, late lunch or early dinner, but in the absence of a better plan, eating seems like a good idea.

Army orders barbecued lamb, yoghurt, rice with raisins, sweet tea. We discuss our next move.

He enters into the spirit of the mission, weighing the risks as earnestly as we do and explaining that if we don't get what we came for, he'll be embarrassed to take money from us.

And then we tour Kashgar, starting with the night market where smoke is rising over the charcoal barbecues and steam over the vats of rice and mutton entrails.

Hawkers sell cubes of fermented yoghurt, and labour over ice cream churns with wooden paddles.

But Army warns that spies are everywhere. And I know enough not to ask sensitive questions in public.

So I look for the people who can converse in Mandarin and we talk about food and hats.

No mention of the fact that only just over the road the imam of China's largest mosque was recently stabbed to death on his way out of morning prayers. Or the riot police and sniffer dogs at major junctions.

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Just along Liberation Avenue under the smiling statue of Chairman Mao the people's square is filling with armoured vehicles.

Our hotel is next door and has bag scanners and doormen in bullet proof vests. Armed police file in and out to use the toilet. A police officer comes to pay us a late night visit. He is not on our side.

Army has made himself scarce, but not before giving advice on the best positions from which to film some of this. We're getting used to thinking he is on our side.

But the problem is he's not. He is actually just a better class of spy, as we discover the next day. How do we find out? It's a long and involved story involving the police revealing information about us that only Army could have told them. Our Chinese producer felt betrayed and sent him packing.

I don't feel so angry with him. This is a place where people grow up playing all sides to survive. Foreign ideas of loyalty and betrayal are just that: foreign.

China is desperately short of Han Chinese who speak Uighur and have Uighur friends.

Army is useful to the state and a diet of news featuring death sentences and long jail terms makes it abundantly clear that the state will crush those who resist.

So if you're Army and you have to double cross someone you're going to choose the BBC because we are not going to imprison you for the offence.

But the experience leaves me sad and disorientated. Forced to rewind and relive each minute with a different set of assumptions.

Image copyright Getty Images Image caption Chinese soldiers march past the Id Kah mosque in Kashgar

Perhaps these are the facts? We thought we were protecting Army from too much information about the place we were going but he always knew far more than we did.

The woman I thought was the girlfriend on the phone was a police handler. And Army was reporting back on all of our plans whenever he had a chance. So everyone at the police checkpoints was expecting us.

We get another driver. He too seems to know more about us than we have told him. We get stopped again by the police. We never reach our destination.

But if life is about the journey not the arriving then so is reporting. Our Xinjiang trip bears fruit in other ways. I have many conversations with Uighurs and Han Chinese that illuminate my understanding of the challenges on all sides.

Our new driver is a danger to those inside his vehicle and out. What's more he gets lost on the way to Kashgar airport so we miss our flight back to Beijing.

At least Army was competent even if he was working for the other side. Some day I'll go back to Kashgar and ask him to tell me some true stories. Too bad I'll never know which of them to believe.

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