The "daisy chain" of nine explosive devices had been hidden at the base of a wall flanking a narrow alleyway. Two deafening blasts came within seconds of each other, spraying shrapnel and debris in an arc as the patrol came alongside. It was the second time in five days that the American and Afghan forces had been targeted in Malajat, a notoriously violent area used by bombers and gunmen as a base from which to strike into Kandahar City.
The attacks illustrate the difficulties faced in attempting to clear the militants out of Kandahar, the birthplace of the Taliban. There are, however, signs that the tide may be turning following a series of military operations in an area which, not so long ago, was regarded as "lost".
The offensive launched yesterday – one of "the most difficult and most important" to be carried out since the start of the war, according to Western commanders – comes at a pivotal time with a Nato summit in November set to shape the future course of action. General David Petraeus, the commander of Nato forces, is also to present his assessment of the campaign to the White House before the end of the year.
The Taliban have been ruthless in their attempts to hang on to their most important and symbolic military stronghold, assassinating over 500 tribal elders, religious scholars, and elected representatives in the process. The killings have been stepped up in the months preceding the Nato campaign.
Many of the murders have been planned and launched from Malajat, a feeder route into the city for insurgents. Three weeks ago a large US force, with a sizeable contingent of Afghan police, moved in, arresting suspects and seizing large amounts of bomb-making equipment and material. "After that we had a bit of a quiet time, no IEDs (improvised explosive devices) no shootings. You couldn't get too relaxed, but considering what the place was like..." Sergeant Robert Yonts said. Then, last week, a bomb went off two feet from him along a pathway, he received minor injuries, his eyes saved by protective goggles. "If it weren't for them I would be blind, simple as that," he said.
In the second attack Sergeant Anthony Gonzalez was with another patrol when the bandolier of bombs began to detonate. "The problem is that they are using very little metal content in the IEDS now, it makes them very difficult to detect," he said.
Colonel John Voorhees, commanding officer of the 504th Military Police Battalion, which is in charge of training the Afghan police in Kandahar, says the scale of insurgent activity has been drastically curbed.
But as the course of this war has shown, winning ground is one thing, holding it is another. Whether the Kandahar mission succeeds or not will depend on whether the Afghan security forces, especially the police, are able to fulfill that function.
The rising incidence of police officers taking part in attacks against Western troops – including the murders of five British soldiers – has also raised concerns about just how far the Taliban has infiltrated its ranks. Lieutenant Colonel Rowley Walker, who served in Helmand, was just one of many senior British and US officers to warn that corrupt police are turning people against the government and "acting as recruiting sergeants for the Taliban".
But preparing the police to take over security remains one of the key planks of the West's exit strategy. Captain John Cromley, of 1st Battalion Combat Team, 4th Infantry Division, said: "I took part in police training in Iraq, in Baghdad and Basra, and we have actually got more people here doing that job. I think that shows how seriously we are taking all this."
Col Voorhees added: "A lot of the successful operations we are seeing now are Afghan planned and led. This is absolutely essential. But at the same time it is also essential that we continue to try and root out corruption.
"It's not just security, we have to establish co-ordination between various branches of the judiciary, enforcement, prosecution and sentencing. It's very demoralising for the police to arrest someone and then see them released because a tribal deal was done."
Haji Zikraya Khan and Mehboob Ali, both members of Kandahar's provincial assembly, had spoken out repeatedly against the Taliban. Last month they paid the price, both of them killed in a bomb attack. Mr Khan's family say that as well as being victims of insurgent brutality they, like many other Kandaharis, have first-hand experience of the rapacious police. "My uncle died because he was speaking out against oppression by the Taliban and revealed how the Pakistanis are supporting the terrorists." said Zulmai Mohammed.
Mr Mohammed's sister, Amina, used to be a clerk in government service. She stopped working after receiving a warning from the Taliban to stay at home. "They do not want women to have any independence. I will know security has improved when I can go back to work. A lot of other women feel the same way. Maybe things are getting better, but we are still afraid, we know women who have been killed for refusing to stop working."
Mr Mohammed conceded that there are some signs of improvement. "The security has improved in the city but there are still Taliban around, and we believe some of the police still sell them information. Things can get bad again. I am a target of the Taliban because of my family, because of what I have said. I must stay careful."
Colonel Ali Shirzaad, the police officer in charge of security in Kandahar City, insisted that most of the active Taliban in the city had been arrested or forced to flee into the surrounding rural areas. Taliban reinforcements, he claims, will come from across the country's border. "It is now well known what the Pakistanis are doing. There is a training school near Peshawar where the ISI (the Pakistani secret police) train people to make IEDs. And they also send their people here, we have arrested many of them."
But there are also powerful figures in the Afghan establishment who exercise a malignant influence, a group of strongmen wielding enormous influence. Major General Nick Carter, the British head of Nato forces in Kandahar, said they had emerged during the Russian occupation in the 1990s. "When you needed a patron, mobs and mafia prevailed, protection rackets were the order of the day. Within that environment it's very easy for the insurgents to intimidate and threaten those associated with the government."
Saif Rahman, a police officer, and his colleagues accept they will face attacks in the future and would like to be better protected against the threats. "We have just one AK [AK-47 assault rifle] between three of us, so we go out on patrols without rifles" he said. "I do not think the Taliban have the same problem."