Royal Marines have begun taking over operations in part of Afghanistan, replacing 16 Air Assault Brigade, who are ending their six-month tour.
Royal Marines have started patrolling in Helmand
Troops from 3 Commando Brigade Royal Marines, based in Devon and Arbroath, are part of a Nato force supporting the Afghan government in Helmand province.
They have begun their mission in the country by joining 16 Air Assault Brigade on joint patrols.
It comes amid a growing debate over the role of UK troops in Afghanistan.
The phased handover to the Marines is taking place over several weeks. The newly arrived troops are expected to remain in the country for at least six months.
'Raring to go'
Speaking after a joint patrol with 16 Air Assault Brigade, Sergeant Bas Shaw, of 3 Commando Brigade, said: "I've served in many parts of the world and this is by far my biggest challenge.
"We have trained hard for this mission and we are raring to go. Days like today when you see the local population and the hope in the eyes of the children make it all worthwhile."
British have been involved in fierce fighting with Taleban forces in Helmand.
Some 40 British service personnel have died in Afghanistan since 2001 - 20 of whom were killed during September.
Last week, the commander of UK troops in Afghanistan, Brigadier Ed Butler, said the Taleban had been "tactically defeated" in Helmand.
And Prime Minister Tony Blair has defended the role played by British forces in the country, after a report said some 90,000 Afghans had been displaced by fighting between Nato troops and Taleban forces.
Mr Blair admitted the population had suffered as a result of the fighting but said they had suffered less than they had under the Taleban regime.