Sir Michael Jackson is skilled at promoting the army

It is an annual event which has been operating for the last 40 years and is taking place at Sennybridge.

But the current international crisis following the terrorist attacks in the US on 11 September have underlined the need for the demanding training.

Short of entering armed combat, it is one of the toughest exercises any soldier can be asked to undertake.

Troops from the US have joined soldiers from Canada, Italy and Holland in Powys which with army ranges at Sennybridge frequently plays host to manoeuvres.

Over 48 hours - deprived of their sleep or rest - a soldier's mental and physical strengths are tested to the limit in the Cambrian Patrol.

Rugged terrain

Carrying an 85lb pack, the teams are asked to negotiate 55km over some of Wales' most rugged terrain. The exercise continues until Saturday.

The commander of British land forces has flown into Wales to witness the patrol.

General Sir Michael Jackson said the exercise was vital proof of Nato readiness and professionalism, praising the operation as an essential part of the Army's current training.

Earlier in the year, soldiers were asked to take on a very different role in Powys when they helped in the disposal of animals slaughtered in the foot-and-mouth crisis which so badly affected the county.