1) Detachment of a legion 
Detachment. provisional unit.
The name (plural vexillationes) given to a group of troops taken from their unit for a specific purpose and then returned once their task was completed. It could be of varying sizes from a century to several cohorts split off from a legion, as seemed to have happened to legio XIV Gemina and legio XX Valeria in Britain. Uses of the designation would…...
detachment of a legion (normally 1,000 men)