Cameron is confronted by the reality of his Afghan problem

On his first day in Downing Street, David Cameron called a meeting of his new National Security Council to assess the situation in Afghanistan, in what was a very public declaration of how seriously he takes the war. The Prime Minister will soon see the reality on the ground when he visits Helmand.

The past few days in this vicious conflict have been particularly bloody. Forty people were killed and 70 injured last night when bomb exploded at a wedding ceremony at Arghandab, near Kandahar. Nineteen Western soldiers, two of them British, have died since the weekend. Yesterday, four US Nato troops were killed when a helicopter was shot down – a worrying development in a conflict where control of airspace is a key part of the coalition's strategy. The Taliban said they blasted the aircraft with a rocket-propelled grenade in Helmand's Sangin district.

A graphic example of how the insurgency has spread across the region came when a Nato convoy en route to Afghanistan was attacked in Pakistan, leaving seven dead.

And in a reminder of how brutal the war has become, the Taliban hanged a seven-year-old boy in front of a silent crowd in the village of Salarwi, having accused him of spying for foreign forces. Insurgents also murdered a teacher and burned down three schools in Zabul, while 20 schoolgirls needed hospital treatment after allegedly being poisoned in Sar-e-Pul province.

General Stanley McChrystal, the commander of Nato and US forces in Afghanistan, has warned that "nobody is winning" a conflict that has reached "stalemate", although he claims the Taliban have "lost momentum". He described the recently recaptured Taliban stronghold of Marjah as a "bleeding ulcer" where security has yet to be properly established.

That a "critical time has been reached" in Afghanistan has become an overused phrase. But there is an undoubted sense of urgency and a renewed diplomatic flurry as the traditional fighting season gets under way, now that the opium is harvested.

Nato defence ministers will meet in Brussels today to try to address the question of just how many more troops member states are prepared to offer for the campaign. The overall commander of the Afghan war, General David Petraeus, and the US Defence Secretary, Robert Gates, met Mr Cameron and others in London yesterday on their way to the Nato summit.

Mr Gates stressed that he did not underestimate the problems faced in Afghanistan. "We can expect a high level of violence in what is likely to be a very difficult summer. In all the coalition countries, the public is going to expect to see some progress by this winter, some sign that we are moving in the right direction," he said.

"If we are making progress, and it is clear that we have the right strategy, then I think people will be patient. But one thing none of the public will tolerate is the perception of stalemate in which we are losing young men."

He added, however, that General McChrystal was "pretty confident" that he could show progress in the next seven months.

To the exasperation of military commanders, Western leaders have laid down time-frames for the Afghan mission which, the soldiers feel, sends the wrong signals to enemies and allies alike. Barack Obama, facing re-election in 2012, set July 2011 as a deadline to start withdrawing US forces. On a visit to Helmand, the British Defence Secretary, Liam Fox, called for a quick exit from what he described as a "broken 13th-century state".

The pressure this puts on the commanders was illustrated when Gen McChrystal visited Marjah. Speaking to US forces, he asked: "How many days do you think we have before we run out of support from the international community? I am telling you, we don't have as many days as we would like ... this is a bleeding ulcer right now. You don't feel it here, but I'll tell you it's a bleeding ulcer outside.

"What we have done, in my view, we have given the insurgency a chance to be a little bit more credible. We said 'we're taking it back'. We came in to take it back, and we haven't been completely convincing."

The next big mission is Operation Hamkai, with the objective of securing Kandahar – birthplace of the Taliban. The generals say it will be the "most difficult and most important" mission carried out by Western forces since the allied invasion nine years ago.

Parts of Kandahar are torn apart by violence and under the influence of the local strongman Ahmad Wali Karzai – brother of the President, Hamid Karzai – and at the mercy of militias and hired guns of security companies. Securing the region is seen as a crucial part of Gen McChrystal's blueprint.

Major-General Nick Carter, who commands coalition forces in the south of the country, said Kandahar was a place where "you have lawlessness, criminality and a culture of impunity". "Landlords and power-brokers are able to rob what they want from the government, take land that is not theirs, and run militias purporting to be private security companies," he added. "This is all compounded by what I would only describe as pitifully weak real governance."

There is confusion about what will happen to Ahmad Wali Karzai. He is widely seen in Kandahar as a powerful figure who instils fear among public figures, including Afghan commanders. According to US sources, his name was put on Nato's "kill or capture list" by an American officer, leading to outrage from the President. Ahmad Karzai is also accused in official US reports of being a drug trafficker. However, there is also the realisation that the West will have to do business with him. Maj-Gen Carter said the President's brother was a "much maligned figure" who could play a positive role in future.

There is also the problem that local leaders are alarmed by the prospect of prolonged violence. During a visit to Kandahar city, President Karzai pledged that no military action would take place without their approval. Western officials insist that he subsequently authorised the mission.

When meeting their President, the Kandahari elders stressed they were left unconvinced by what transpired at Marjah. The Nato mission there was supposed to embody a new strategy in which newly-trained Afghan forces would move into captured areas to provide security. Too often in the past, ground taken at a cost of lives has been allowed to slip back into the insurgents' hands because of a lack of troops.

Many locals say the Taliban have not gone away. Haji Mohammed Hassan, a tribal elder, fled Marjah for Helmand after he was threatened three weeks ago. "There was no security" he insisted. "By day there is government, by night it's the Taliban." It is an established and highly effective Taliban tactic to eliminate tribal leaders who stand up to them. Nato and Afghan troops were supposed to prevent this in the recently recaptured areas.

"Two tribal elders were taken from their homes and had their heads cut off," said a shopkeeper, Jawad Ahmed Ali. "Of course, this makes the people very afraid. [The Taliban] do not want the Afghan government established here. They are showing the people the government and foreign forces cannot protect them. But these men must be protected, otherwise the Taliban will win. We want to see the Afghan army here, but we do not want the police."

Suspicion of the police among locals remains a major headache for Nato. British commanders returning from Helmand have warned that corruption and abuse of power by the police force has alienated people and driven some to join the Taliban. Lieutenant-Colonel Roly Walker, commanding officer of 1 Battalion Grenadier Guards, who had five men shot dead by a policeman they were training, said the Afghan officers were one of the "biggest obstacles to progress" and one of "the reasons for the insurgency".

British and US officials stress that despite all the problems, progress is being made. Indeed, Lt-Col Walker also pointed out that villagers were generally welcoming towards the new force of more professional police. And, three-and-half months after Marjah and its hinterland were wrested from the Taliban, families have returned, the market is thriving and the governor has begun to build an administration.

Continuing on the slow path to peace, they stress, needs resolution and commitment. Gen Petraeus told a conference in London yesterday that "as was the case in Iraq, the scale of the British contribution in Afghanistan is such that the coalition cannot succeed without you".

However, the US and UK approach in Iraq was not always united. When British forces pulled out of Basra against Washington's wishes, US Marines were forced to take over. Mr Cameron must decide whether British troops in Afghanistan will stay the course, despite the mounting loss of lives, or whether there will be "Basra moment" in this conflict as well.

Conflicting strategies

General Stanley McChrystal

US commander of Nato forces in Afghanistan

Likely to be held responsible for the success or failure of the Afghan mission. President Obama has backed his "surge" strategy, against the wishes of vice-President Joe Biden, but has also stipulated that drawdown of US forces should start from July 2011. Gen McChrystal has expressed his concern about the slow pace of establishing security in Marjah.

General Sir David Richards

Head of the British Army

Many of the ideas he put forward in 2006 when Nato commander in Afghanistan are now being implemented. He has been an advocate of British troops staying in the fight until Afghan forces are trained up, holding that leaving prematurely will cause problems throughout the region. He and other commanders, it is believed, would like a feasibility study of what the future holds for UK forces in Afghanistan.

Liam Fox

UK Defence Secretary

His declaration that British troops should make a quick exit from a "broken 13th Century state" led to criticism. He has since repeatedly stressed the commitment of the government to Afghanistan. However, he has ruled out an American proposal for UK forces to move from Helmand to take over from the Canadians in Kandahar.

Robert Gates

US Defence Secretary

He was one of those instrumental in persuading President Obama to back Gen McChrystal's strategy. He has stressed the need for staying the course in the conflict but has also warned that "the public in the Coalition countries wanted to see progress. One thing none of the public will tolerate is the perception of stalemate in which we are losing young men."