Roulement is a term used by the British Army to signify major combat units (usually battalion strength) that are deployed on short tours of duty, normally for six months.
It is also used in the wider British military to mean the deployment of a strength of personnel on continuing operations.
The British Army has historically deployed infantry battalions for 6-month and 24-month roulement tours of Northern Ireland.
crewman cost an estimated £500,000 to train and skills were lost during any longer tour.
[1][2] The British Army deployed roulement units to Afghanistan as part of Operation Herrick.