The attack came just 12 minutes after leaving the base – short, staccato bursts of Kalashnikov fire hitting the open-top, seven-ton truck. A shot went through the driver's windscreen, others flew over our heads, forcing us to huddle down as more bullets smacked against the side. The Taliban were hitting back as military convoys rolled towards one of their main strongholds in Helmand.
This was the first big offensive since the announcement that 30,000 more US troops were to be dispatched to what is now very much Barack Obama's war. The mission had been postponed while intense political debate on the reinforcements took place in Washington. What happens here, and in other operations which will unfold in the coming months, will determine whether the surge, the strategy which curbed the ferocious violence in Iraq, has a chance of success in Afghanistan.
The Independent accompanied a force of around 1,500 – two-thirds US marines, the rest British, Danish and Afghan – as it launched Operation Khareh Cobra, "Cobra's Rage" in Pashto. Their target was Nawzad, once the second largest town in the province, which passed into Taliban hands two years ago. Since then, the town had become an important arms and opium storing centre for the insurgency, as well as a "blooding ground" where young jihadists cut their teeth. One strip of land, known as "Pakistani Alley", has been a transit point for foreign fighters, mainly, as the name suggests, Pakistanis, to other parts of Helmand.
The doctrine presented by General Stanley McChrystal, the US commander of Nato forces in the country, calls for places like Nawzad to be recaptured and protected. British forces had been involved in fierce combat with the Taliban here. But there were never enough troops to hold the ground. The massive American influx into southern Afghanistan, with 9,000 more marines due to join 11,000 already here, is designed to change that.
The sheer size of the operation for Nawzad made it impossible to disguise the build up of forces. Interception of Taliban radio traffic showed commanders speculating about whether the attack would be towards the south or the east; in the end, it came from all sides, with an air assault preceding an armoured thrust. British troops formed a screen to prevent militant fighters escaping towards Musa Qala.
Camp Cafaretto, the US forward operating base, has a number of British connections. One of those who planned the operation, Captain Andrew Terrell, had spent two years on attachment with the Royal Marines in England. There is also a resident Brit, a lieutenant, John (who did not want his surname published) from south London, who was an archaeologist before joining the marine corps. "I had an American girlfriend who was in the Navy, and then 9/11 happened and I decided to join. I don't have any problems being here. The people want security. That is what we are trying to provide," he said.
Some US servicemen said they felt a sense of being involved in a moment in history because of the timing of the mission so soon after the presidential decision. There was also a sense that this was payback time. Their comrades had been killed by booby traps in the district centre, and the use of roadside bombs and mines made the Taliban, in the eyes of the American forces, an enemy as cowardly as it is ruthless. Chaplain Michael Taylor told the young marines as they prepared for combat: "You are the instrument of the Lord's wrath and indignation. Be strong in administering justice. As you face death, whether you deal it out or receive it, it is better to be true to yourself than be a coward who hides at home refusing to protect the innocent." Then there was a warning to remain true to the mission's ideals. "Be pure in your justice,' the chaplain said. "Examine if we have become the men we hate."
Two hours later, there was more firing in our direction from surrounding hills as we scrambled down from the trucks at a rendezvous point. Further along came the deep booms of "Mic-Lics", line charges cutting channels through ground pitted with roadside bombs and mines.
The next hours were spent with Lima Company of 3rd Battalion, 4th Marines, as they smashed through walled compounds in an area called the Water Margin. Watching a door blown away, Lieutenant Dan Frank said: "It's not a pretty sight, but it's the way to get the job done. My men are the best guys you would want beside you in a fight, but I am not sure I would want many of them to date my sister."
What were the chances of reconciling Taliban fighters, part of Nato's new strategy, a young marine was asked. "If he genuinely wants to come over that's fine," he said. "But if he keeps fighting, well we've just got to take care of him, kill him."
A unit coming down from the north came across Taliban attempting to flee the closing trap. The fighters, in groups of two and three, slipped through the narrow alleyways, spraying shots as they went. The American forces returned fire, attempting to box their enemy into groups, and then called in air strikes; the missiles hitting with deafening noise, throwing up dense swirling clouds of dust and debris.
The marines found dozens of bombs and booby traps in the Water Margin. A search revealed mortar rounds in a building at the entrance to the village of Changowlak. The house owner, Izatullah, was taken away protesting his innocence, someone had left the weapons in his yard, he said, without his knowledge.
Were there Taliban fighters in the village? A group of locals were asked. "They don't stay here, but they come at night and they ask for food and stay," began Jamal, 16, before being angrily interrupted by Mohammed Kabir, 62. "Don't listen to him. There are no Taliban here, no Taliban at all," said the elder. "Listen, we get pressure from both sides. The Taliban create trouble and then we get problems from the foreigners sending their aeroplanes to carry out bombings. Why don't they build us roads and hospitals? That is what we need."
An Afghan soldier, Mainullah Khan, shrugged. "You cannot blame him for denying the Taliban have been here. These soldiers will go away, but he has to live here and the Taliban could come back one day." But are the Americans not staying on? "That is what the British said and then they went away. People will judge for themselves."
Akhbar Jan, a farmer, piped up. "This is our land, we need it to live,' he said. "They are using this for fighting. We will accept that if it means that then we get some benefits. We do not want the Taliban here. We do not want any more war. There has been too much violence, too much."
Back at the US base, Colonel Martin Wetterauer, the commander of 3rd, 4th Marines, was asked how his mission reflected on Mr Obama's decision to send reinforcements. "We have shown that, with adequate numbers of troops, you have more options on the battlefield," he said. "You can take ground quicker and you can hold it. We can then bring in the district governor and start reconstruction, and then, hopefully, people can return to a normal life."