Man on a mission: US defence secretary Robert Gates is still hungry for the fight in Afghanistan

As his Black Hawk helicopter headed to Forward Operating Base Joyce, Robert Gates, the Pentagon chief, was able to look down on the Hindu Kush mountains, a route for invaders and sanctuary for warlike tribesmen back to Alexander the Great.

Places like FOB Joyce, deep in Kunar province in eastern Afghanistan, underline the reason why Mr Gates is pressing President Barack Obama for more time to wage a war that has already lasted longer than the period of American involvement in both world wars.

Treading a careful line between highlighting the "tough fight" being waged by American-led coalition forces and trumpeting his new conviction that "our strategy is working", Mr Gates appears poised to prevail when the White House finalises its Afghanistan review this week.

After meeting Mr Gates in Kabul, General David Petraeus, commander of Nato forces in Afghanistan and the man who oversaw victory in Iraq, said the surge had "arrested the momentum of the Taliban" in much of Afghanistan but the enemy still enjoyed freedom of movement in many areas.

The review comes a year after Mr Obama's West Point speech that ordered a surge of 30,000 US troops, bringing America's total force to 100,000, compared to just 20,000 at the start of 2009. It is likely to conclude that slow but steady progress is being made and now is not the time to change course.

The new Nato deadline for transferring security control of the country to the Afghans is the end of 2014. Whether the Taliban can be defeated by then remains an open question, as Mr Gates would probably admit.

Less than three miles to the west of FOB Joyce, through the heat haze, the US Defence Secretary could see the Hindu Kush peaks that mark the Pakistan border, situated on the old Durand Line drawn up by the British in Victorian times to divide the rebellious Pashtun people.

To the south of FOB Joyce is the Tora Bora cave complex, a redoubt of the Mujaheddin against the Soviets in the 1980s and the place where Osama bin Laden escaped from US Special Forces in 2001.

To the north was the Korengal Valley, which American troops recently abandoned after the loss of 42 troops there. The valley saw countless incidences of heroism, including one that prompted the award last month of the first Medal of Honour to a living recipient since the Vietnam War.

Mr Gates, the only United States Cabinet member to have served both President George W Bush and Mr Obama, was visiting military bases throughout Afghanistan to establish some ground-level truth.

After touching down on FOB Joyce's dusty Landing Zone, surrounded by sandbags and flanked by watchtowers, Mr Gates presented six Silver Stars, the third highest American gallantry award.

The first, to Lieutenant Stephen Tangen of Naperville, Illinois, cited "valorous actions against a heavily fortified enemy" while rescuing wounded Afghan soldiers under "devastating fire" and ensuring his platoon's survival.

In a briefing that began with a PowerPoint slide entitled "The Problems in Kunar" and depicting "Why 'They' Have Gotten Stronger", Mr Gates was told by Lt Col J.B. Vowell, the battalion commander, that his men were battling a "surge in fighters".

Their "tenacious" enemy was using Afghan government corruption as its chief recruiting tool while the "survival culture" of people keeping a foot in both camps and a complex system of patronage undermined American attempts to secure allegiances.

Over the summer fighting season, Lt Col Vowell said, attacks had risen by 200 per cent, while a lack of American forces in the valleys had allowed Taliban forces to flow in from Pakistan.

While the Americans had achieved success in the summer's Operation Strong Eagle, the Taliban had launched their own offensive - Operation Al Faath, the Arabic word for "victory" taken from the Koran.

The Taliban, Lt Col Vowell said, viewed itself as winning because of the withdrawals from the Korengal Valley and four other remote locations. Its strategy was to maximise its gains so that it could cut the best possible deal "when the music stops".

In Mr Obama's West Point speech, he declared that July 2011 would be the date when US forces would begin to be withdrawn. Within Afghanistan, that was widely interpreted as the moment when the music would stop.

Now that Nato has embraced the end of 2014 as the completion date for the handover process, Mr Gates and Gen Petraeus have effectively bought more than three years of extra time.

The message to the Taliban, Mr Gates said at FOB Howz-e-Madad in Kandahar last week, was that "if you think this is over come next summer, think again".

Up at FOB Joyce, Maj Gen John Campbell, commander of the 101st Airborne Division, the job that first propelled Gen Petraeus to international attention during the Iraq invasion of 2003, argued that the July 2011 deadline had been counter-productive.

"For too long, people got this July 2011 thing out there and even the ANSF [Afghan National Security Forces] would say, 'You're leaving'." But now the 2014 date was operative, he said, the message was: "No, we're not leaving. This is an enduring relationship. We're here with you."

Both Gen Campbell and Gen Petraeus emphasised that although Mr Obama's surge had been ordered a year ago, the final troops had only just got into place. Gen Campbell said that "every single day we're either dropping bombs or Hellfires" in the nearby Pech Valley.

"It's very, very kinetic. The people don't want us up there but they don't want the Taliban either. They want to be left alone. So we've got to set the conditions at some point to be able to bring our forces out of there and reposition wherever the most people are."

He indicated that the 101st Airborne had yet to transition to a counter-insurgency strategy in Kunar and surrounding provinces.

"You've got to start with security first. You can't just go in and do governance before security. You can work some in tandem but you've got to get the security... It's going to take some time to work that piece."

Pakistan's double game and role in harbouring members of the Taliban's dangerous Haqqani network could prolong the conflict, he conceded. "They've sanctuary in Pakistan, we shouldn't make any bones about it. They go back and forth across the border."

At the same time, some Taliban elements are being pushed into Afghanistan as a result of increasing pressure from Pakistani forces. Lt Col Vowell said. During Operation Strong Eagle, he conducted complementary actions with his Pakistani counterpart on the other side of the border.

Mr Gates said that "in the east what we're engaged in is a disruption activity and a blocking activity to stop the Taliban from coming across the border" whereas in Kandahar and Helmand in the south "it's a different strategy of clearing the Taliban out of populated areas and then holding those areas".

After FOB Joyce, Mr Gates flew to FOB Connolly in neighbouring Nangahar province. There, he met privately with soldiers who lost six comrades shot dead last month by a rogue member of the Afghan Border Police.

A soldier at the meeting said that Mr Gates had wept as the troops had recounted their experience.

In Helmand, at the US base Camp Leatherneck, Mr Gates was given a much rosier situation report. After meeting him Maj Gen Richard Mills, the divisional commander for Helmand (with overall responsibility for the bulk of Britain's 10,000-strong force) said the Taliban was now making its last stand at Sangin.

Gen Mills told The Sunday Telegraph that that it would be "a mis-statement that the UK did anything but a satisfactory job" in Sangin, where 106 of the 346 British troops who have died in Afghanistan were killed, before the district was handed over to US Marines in September.

"The enemy's fighting with desperation. This is his last toehold. He cannot be kicked off this thing and so he's fighting with a real of sense of willing to die in place - and we're giving him that opportunity."

At every stop, Mr Gates addressed the troops, posed for a photograph with each one (on occasions, more than 350 lined up) and told them that as "the guy that signs the order to send you here" he felt a personal responsibility for every one of them.

In FOB Joyce, the normally unemotional Pentagon chief ended by telling the 101st Airborne soldiers gathered: "I feel the sacrifice and hardship and losses more than you'll ever imagine. You doing what you do is what keeps me doing what I do. I just want to thank you and tell you how much I love you guys."

Mr Gates, a veteran of the Cold War who began his career in the CIA before serving in a string of Republican administrations and ending up as CIA Director, has indicated he will step down next year.

Pentagon officials say that he wants to ensure that the Afghan war strategy is in place and is working before he leaves. Judging by his carefully calibrated words in Afghanistan, he believes that he is close to that point.

Some senior military figures, however, fear that Mr Obama, now politically weakened and beset by domestic difficulties, never fully bought into his own surge strategy and is a reluctant war president whose instinct remains to leave Afghanistan as soon as possible.

Although the generals are anxious to portray the clock as only being started recently with the arrival of the last surge troops, for the American public the war has been dragging on for nearly 10 years with little sign of imminent victory.

Gen Campbell seemed to accept that those back home had yet to be persuaded that it was worth remaining in Afghanistan, even as he was intent on reassuring Afghans that America was in for the long haul.

"We can sell Coca Cola and Kentucky Fried Chicken and Burger King everywhere in the world but we can't tell people back in the US what the hell we're doing here."