By Ian Pannell
BBC News, with British troops in Helmand province
British troops are trying to take land from the Taliban - and hold it
For the British, it is Operation Panther's Claw. For US Marines, it is Operation River Liberty.
They are two separate offensives, but they are also closely co-ordinated and inextricably linked.
They are part of the most ambitious combat campaign in Helmand since British troops were first deployed to this southern province four summers ago.
Ostensibly, this is about making the area safe for presidential elections next month. But it is also about trying to change the momentum - creating a sense that security in Afghanistan is actually improving.
Since the US-led overthrow of the Taliban in 2001, the movement has regrouped and evolved to become a deadly guerrilla force.
British troops have been fighting that force in Helmand since 2006, but most now concede they have reached a stalemate.
In the last few weeks, 11,000 US marines have joined the battle, and some 4,000 of them are taking part in Operation River Liberty to clear the insurgents from key southern districts.
British forces are conducting a similar offensive a few kilometres further north.
If they are successful it will significantly increase the amount of populated land under the control of the government in Helmand.
This is a high-stakes confrontation that will have an impact far beyond this dusty province.
Helmand has been the most difficult of all provinces for coalition troops. It is where the insurgents have their largest and most virulent presence.
Violence and death have been the hallmarks of the last few years in Helmand and the latest figures show there are now more than 10 attacks every day here.
This offensive is also a crucial test for President Barack Obama's strategy for the region.
If the surge in troops is to work, if the government writ is to run across the country, if Nato is to ever have a chance of leaving Afghanistan with dignity, then the troops out on the ground must turn the tide against the insurgency in Helmand.
For the Taliban, this is also a significant challenge. Despite being routed in 2001, they have managed to re-emerge as a mortal danger to British troops deployed here.
More than 170 personnel have now lost their lives in Afghanistan, most at the hands of the Taliban in Helmand.
In the last three years, the Taliban have benefited from volunteers from across the Muslim world and hundreds of local recruits, as well as the limits of Britain's ability to control large swathes of territory here.
Publicly, the insurgents remain upbeat, insisting they have not lost ground. But these combined operations represent the most sustained and significant assault against the Taliban since 2002.
This summer could prove decisive for all parties; the Karzai government in Kabul, the Nato-led mission and the Taliban.
Operation Panther Claw started a little over two weeks ago. Operation River Liberty is just a few days old. Both will take time to clear their respective areas of insurgents.
Col Rupert Thorneloe and Trooper Joshua Hammond died this week
Even if they succeed, which is far from guaranteed, then they must also try to win over the local population.
Thousands are believed to have fled the fighting here. There are no reliable figures for exactly how many, but a large camp for displaced people has appeared on the outskirts of the regional capital, Lashkar Gah.
Those that remain say they are too poor to go elsewhere, or they simply refuse to leave their properties untended.
Convincing them that the local governor, backed by foreign troops, is the best bet will not be easy.
There is an instinctive reticence towards foreigners here. Although there is little support for the Taliban, there is little regard among ordinary Helmandis for British or American troops either.
Nor are people anxiously awaiting the return of law and order
Helmand in July is searingly hot, dry and dusty. The lives of people here are untouched by modernity and they have never answered to central government in Kabul.
These military operations mark the start of the most concerted effort to date to change. It is a daunting challenge for all concerned.