American, British and Afghan troops have launched the largest offensive in Afghanistan since the Taliban were overthrown in 2001.
We trace the major events of Operation Moshtarak - meaning "together" in Dari - as Nato and the Kabul government try to oust the Taliban from strongholds in southern Helmand province.
DAY 6: 18 FEBRUARY
Taliban militants battling coalition troops in Marjah, Afghanistan, are
running out of ammunition, Nato officials say.
A BBC correspondent in Kandahar says that from eavesdropping on Taliban communications, Nato understands militants have called for support.
Troops are due to push into south-west Marjah in the coming days
Nato officers told BBC security correspondent Frank Gardner in Kandahar that the resistance they were currently encountering was coming from small, disjointed but determined groups of fighters.
In the next few days, US Marines and Afghan government troops are due to push into south-west Marjah, which is believed to be an insurgent stronghold.
But the head of the council for tribal elders in Helmand told BBC Pashto that the long-term security of the area depended on locals being involved in policing.
He added that the people of Helmand felt isolated from Afghanistan's central government.
DAY 5: 17 FEBRUARY
An Afghan general says Taliban militants are increasingly using civilians as
"human shields" as they battle against a joint Afghan-Nato offensive.
US Marines have come under heavy fire in Marjah
Gen Mohiudin Ghori said his soldiers had seen Taliban fighters placing women and children on the roofs of buildings and firing from behind them.
US Marines fighting to take the Taliban haven of Marjah have had to call in air support as they come under heavy fire.
They are facing sustained machine-gun fire from fighters hiding in bunkers and in buildings including homes and mosques.
A local journalist based in Lashkar Gah also told BBC Pashto that Taliban fighters remained in many residential areas of Marjah and were defending their positions with heavy weapons.
"Whenever they launch an attack, the Taliban take refuge in civilians' homes," Jawad Dawari said.
DAY 4: 16 FEBRUARY
The commander of British forces in southern Afghanistan says a missile that struck an Afghan house killing 12 people on13 February
hit its intended target.
While British and Afghan troops were advancing, US progress was hampered
Maj Gen Nick Carter says initial Nato reports that the missiles had landed about 300 metres off their intended target were due to "the fog of war".
US forces face some resistance around the Taliban haven of Marjah, with their progress being hampered by sniper fire and improvised explosive devices (IEDs) in some areas.
British and Afghan troops are reported to be advancing more swiftly in the nearby district of Nad Ali.
Meanwhile, officials say the Taliban's top military commander and leading strategist, Mullah Abdul Ghani Baradar,
has been captured in a joint US-Pakistani operation in Karachi.
DAY 3: 15 FEBRUARY
US marines and Afghan troops
continue to meet resistance in Marjah.
In the north of the city an armoured column is reported to come under fire from several sniper teams while marines try unsuccessfully to clear Taliban fighters from a bazaar in the centre of the city.
The situation for the British and Afghan troops
further north, in Nad Ali, now appears to be quieter and more stable than in Marjah, says the BBC's security correspondent, Frank Gardner, in Kandahar.
Afghan Brig Gen Sher Mohammad Zazai says coalition troops have largely contained the insurgents in Marjah and Nad Ali.
Nearly 1,000 families displaced by the fighting have arrived in Helmand's capital, Lashkar Gah, a provincial official says.
DAY 2: 14 FEBRUARY
Twelve Afghan civilians are killed in Marjah
when Nato rockets hit their house.
Officials say two rockets fired at insurgents veered off course.
The coalition forces in Marjah report sniper fire and a large number of home-made bombs, or IEDs.
US officials say their troops are in the "majority" of the city but are beginning to meet more determined Taliban resistance in some areas.
The Red Cross sets up a first aid centre in Marjah and says it has treated dozens of residents injured in the fighting.
Nato and Afghan officers begin to hold meetings with tribal leaders, as part of plans to bring in hundreds of Afghan police in the coming days to help secure the captured areas and restore government rule.
DAY 1: 13 FEBRUARY
More than 15,000 US, UK and Afghan troops are dropped by helicopter in Marjah and Nad Ali in the early morning as
Operation Moshtarak begins.
US and Afghan troops in Marjah come under sporadic rocket fire and heavy machine-gun fire. One US marine is killed by gunfire, but Nato officials say the troops make good progress.
A British soldier is killed by an explosion in Nad Ali, although military officials say overall resistance from the Taliban there is light.
Taliban commanders say they have pulled back to avoid civilian casualties.
Many residents have also fled the area, heeding Nato pamphlets that warned of the coming offensive.