Kate Middleton has assisted in a training exercise with the Irish Guards regiment of the British Army.
She braved snow to help administer first aid to a wounded soldier as part of an exercise in southern England.
Prince William's wife joined members of the 1st Battalion Irish Guards for training, simulating a situation where they had been on a foot patrol when they came under fire.
The Irish Guards, formed by Britain's Queen Victoria in 1900, are experts in infantry combat.
Their specialisms include reconnaissance, engaging enemy troops with machine guns and mortars and anti-tank operations.
The Irish Guards are controversially known throughout the British Army as 'The Micks'.
Its soldiers - who are recruited from the island of Ireland, the UK and beyond - guard Britain's royal family.
St Patrick's Day is the traditional celebration of the Irish Guards.
The exercise with Kate Middleton involved a soldier suffering a gunshot wound to his lower left leg and being evacuated from the scene by his colleagues.
Kate assisted in the drill, administering first aid and applying a tourniquet.
The 'injured' soldier was then moved onto a stretcher. Kate helped with assessing him for further injuries to his torso.
Kate, who is Colonel of the Irish Guards, was visiting the troops for the first time since receiving the honorary appointment last year when she took over from her husband.
She was also taken on a tour of a training area.
Kate was told about the work the battalion has undertaken recently - including meeting members who have been deployed on security work in Africa and training park rangers on counter-poaching operations.
She wore a green combat uniform emblazoned with the rank of colonel, and viewed several different types of weapons used by the regiment.
Reporting by: IRN