Operation Moshtarak: Assault in Helmand province

US, British and Afghan forces have begun a major offensive in Helmand province.

BBC News looks at the offensive and its ultimate target.

OPERATION MOSHTARAK

Operation Moshtarak, which means "together" in the Dari language, involves more than 15,000 Nato and Afghan troops.

FORCES IN MOSHTARAK Afghan National Army and police 1 Grenadier Guards Battle Group 1 Royal Welsh Battle Group Scots Guards US Marine Corps Various Isaf-controlled units

The joint offensive in central Helmand involves American, Canadian, British, Danish and Estonian forces.

Nato says Afghan forces have been closely involved in planning, and are playing a central role in the operation.

Led by the US Marine Corps, it is the first major attack since the US sent 30,000 extra troops to the country.

The Marines are leading the main thrust of the offensive, focusing on Marjah, an insurgent and drug-smuggling stronghold, south of Helmand's capital, Lashkar Gah.

In support, British forces are securing nearby Nad Ali district, to the north of Marjah.

The idea is to clear the area of insurgents and allow forces to work with local institutions to bolster reconstruction and provide support for the rule of law.

The difference this time is the nature of the publicity surrounding the push. Troops have been working with tribal elders to prepare the way for the return of Afghan police.

Marjah is a major population centre

Analysts say it epitomises the new "counter-insurgency" approach of US and Nato commander Gen Stanley McChrystal.

Local people were warned about what was to come so they could protect themselves and stay away from fighting.

Troops are operating from Camp Bastion, Camp Leatherneck and also from Kandahar bases.

THE TARGET: MARJAH

The US military has for some time signalled that it plans to take on the Taliban in the town and district of Marjah. It has been targeted before.

It lies in the heart of the poppy cultivation belt of southern Afghanistan - the centre of opium production.

It is known as the "green zone" of Helmand - a strip of irrigated land along the main river. It is also known for the volatile insurgency that has bred in the district.

In the 1950s, US development workers built the town to populate the arid desert of southern Afghanistan. They helped to irrigate the area by constructing canals.

US marines and Afghan troops are leading the attack on Marjah

But the district has more recently become a haven for hundreds of Taliban fighters and is considered an assembly centre for roadside bombs.

Dubbed a "festering sore" by a senior US Marine commander, Marjah has for a while been regarded as one of the last main insurgent-controlled areas in southern Helmand.

Before the offensive, US officials estimated there were between 400 and 1,000 Taliban - including some foreign fighters - in an area with a civilian population put at about 125,000.

However, not all the Taliban are believed to be diehards, and those paid to fight may just prefer to melt away in the face of superior force, military officials say.

Marjah is about 40km (25 miles) from the strategically significant provincial capital Lashkar Gah, and is one of the largest population centres in Helmand.