Royal Marines Commandos from Devon have left their base in the county to be deployed to Afghanistan.
The Marines will be supporting development of the region
A total of 150 men from 42 Commando, based at Bickleigh, near Plymouth, are going to the volatile Helmand province.
The Marines will be the first combat troops to go following an announcement on 26 January that about 3,300 British troops are to join Nato's force.
Their main tasks will include tackling suicide bomber threats and to protect army and RAF engineers in the area.
Col Gordon Messenger, in charge of the deployment, said earlier this month that the troops would not "hunker down" and wait for suicide attacks.
They will provide security to help Afghan forces fight the drugs trade in the province, one of the main poppy-growing areas.
They will also be protecting RAF and Army engineers setting up a base at Lashkar Gar, the capital of Helmand province.
Lt Col Ged Salzano, commanding officer of 42 Commando, said: "The company group is robust enough to look after itself and protect the engineers.
"Conditions are expected to be tough but 42 Commando are well prepared for the task."
Troops from 42 Commando have just returned from the Bagh region of Pakistan where they assisted in the earthquake disaster relief.
Armed Forces Minister Adam Ingram said: "I pay tribute, once again, to the commitment and versatility of 42 Commando who have just returned from Pakistan on humanitarian relief work.
"42 Commando will now deploy to Afghanistan with the crucial role of supporting the set up of a base in anticipation of UK Forces fulfilling ISAF's mission in Helmand."