The term 'Drill Sergeant's 'ONE'' can be summarized as a three-letter acronym, HUP, which stands for 'Halt, Unit, Prepare'. This is a command used by drill sergeants to get their troops to stop what they are doing, form up into a unit, and prepare for further instructions. It is a way for the drill sergeant to quickly and efficiently get the attention of the troops and have them ready for whatever comes next.