By Frank Gardner
BBC News, Kandahar airbase
Afghan and Nato troops are clearing the ground for police to move in
It's day three of the joint Nato-Afghan military operation codenamed Moshtarak - meaning together or shared - and the forces have experienced both successes and setbacks.
After inserting thousands of troops by helicopter into Taliban-held territory in the early hours of Saturday morning, Nato commanders say they are so far achieving their military objectives.
But on Sunday things went badly wrong when a rocket fired by coalition troops in the US taskforce area of Marjah missed its target, hit a building and killed 12 Afghan civilians.
Nato's commander in Afghanistan, US Gen Stanley McChrystal, immediately suspended all use of the rocket system involved while Afghan President Hamid Karzai ordered an investigation.
Nato was quick to apologise but the incident will not have helped its efforts to win over the trust of the local population, something that lies at the heart of this whole operation.
Meanwhile US, British and Afghan forces are having to cope with an unexpectedly high number of improvised explosive devices (IEDs) planted by insurgents.
For all the hi-tech aerial surveillance, infrared cameras and sophisticated eavesdropping at Nato's disposal, its forces on Operation Moshtarak appear to have underestimated the scale of the problem of these roadside bombs, which have become the Taliban's weapon of choice.
Using easily obtainable components like ammonium nitrate fertiliser pellets, plastic jerry cans and two pieces of wood, the insurgents have managed to slow the troops' advance, especially around Marjah.
The situation in the British taskforce area of Nad Ali now appears to be quieter and more stable than in the US taskforce area in Marjah, to the south-west.
Distinguishing insurgents from civilians is a challenge for coalition forces
British patrols in the run-up to this operation had already established a presence on the ground before the helicopter lift of extra troops at the weekend.
The US Marines, by contrast, have had to go into virtually uncharted territory, notorious as a centre of the illicit opium processing industry.
This means that the British taskforce area will probably be ready sooner for what commanders are calling the "holding" phase of Operation Moshtarak - the setting up of joint Afghan-Nato patrol bases and the introduction of hundreds of newly-trained Afghan police.
Known as the Ancop (Afghan National Civil Order Police) they received more than twice the amount of training at four months than the much criticised ANP (Afghan National Police) who in many cases are recruited, badged and put on to the streets with no training at all.
Reports are rife of the ANP setting up checkpoints on roads to demand money from citizens at gunpoint, which is exactly the sort of bad governance that helped give birth to the Taliban movement in 1994.
Leaders flee north
So where are the Taliban in all this?
Nato believes that Taliban leaders in central Helmand fled some time ago to Pakistan while those insurgents that have chosen to stay and fight are believed to be concentrated in Marjah.
Many of those in the British taskforce area of Nad Ali are thought to have either put down their weapons or retreated northwards towards the town of Sangin.
The assessment of Nato intelligence officers is that insurgent resistance to Operation Moshtarak is disjointed and in pockets.
They believe the Taliban may be holding off from launching attacks for the next few days while they wait to see if Nato and its Afghan government allies are staying or leaving.
Nato and Afghan commanders are adamant that they now have enough troops to hold the ground taken and establish local governance.
But Afghan villagers are likely to remain sceptical. The last time coalition forces went into Marjah was in May last year and they left after four days.