A trooper unit with the or rank benefits from backup if it is at and has LOS to the unit leader of a unit that provides backup. A unit must meet the following requirements to provide backup:- The unit has the rank.
- The unit is a trooper unit.
- The unit does not have a number of suppression tokens equal to or greater than its courage.
When a unit that is benefiting from backup is attacked by a ranged attack and the attacking unit’s unit leader is beyond of it, it may cancel up to two results during the Modify Attack Dice step of the attack sequence.A unit with the Guardian X keyword cannot benefit from backup and ignores the rank requirement to provide backup.[Source]