Soldiers from 40 Commando have already been on duty in Afghanistan in guarding Bagram airport.

Now their fellow troops in 45 Commando will have a more offensive role in trying to root out the remaining al-Qaeda forces still active in the Afghan mountains.

It is not the first time the unit, commanded by Lieutenant Colonel Tim Chicken, has been called to the front line in recent years.

1994 saw 45 Commando deployed to the Kuwaiti border to deter Iraq, for example.

Between combat and peacekeeping missions, the vast military exercise in Oman topped up skills already honed in arctic training exercises.

45 Commando is one of the three units that make up 3 Brigade, whose troops total about 3,500 troops divided into three battalion-sized units of infantry soldiers.

The other battalion-sized units are 40 Commando based in Taunton and 42 Commando in Plymouth.

The origins of the brigade can be traced back to the formation of the first commando units in 1940, at the request of then-Prime Minister Sir Winston Churchill.

He called for "specially trained troops of the hunter class, who can develop a reign of terror down on these [enemy occupied] coasts".

The emphasis was on daring, tough soldiers, who were extremely proficient in small unit tactics and stealthy approaches - often upon heavily defended targets.

Like other parts of the brigade, 45 Commando saw almost continuous action - returning to the UK in 1967 after 24 years of operational service abroad.

Those years saw the brigade take part in the Anglo-French Suez invasion in 1956, an operation which saw the first use by UK forces of helicopters in the assault role.

Its troops were amongst the first to be drafted into Northern Ireland in 1961 and have served there almost every year since.

Pivotal moment

In 1982 the brigade engaged in the most important conflict in its history - the Falklands War.

With other components of the Royal Marines, the brigade sailed for the Falkland Islands within five days of being warned for operations, and staged an extremely successful amphibious landing.

The brigade fought throughout the six-week campaign in mountainous territory, which culminated with the surrender of the Argentine forces on the island.

The Royal Marines' success in this conflict prompted a defence ministry rethink on budget-cutting plans which could have spelled an end for the amphibious forces.

And in post-Cold War conditions, the brigade has been keeping busy.

Its troops were deployed to Bosnia-Herzegovina throughout the 1990s.

In spring 2000 the brigade headed out on HMS Ocean to help evacuate British nationals from Sierra Leone.

The same year, the brigade spent six months in Kosovo in the same year, leading multi-national troops on Operation Agricola IV. In Operation Safe Haven in 1991, 45 Commando protected Kurdish Iraqi refugees stranded in the mountains between Northern Iraq and Turkey.

And it continues to carry out regular Arctic climbing and mountain exercises in Norway - the only British troops to do so - while jungle warfare has also been on its training regime.