Rearguard (noun)

1. A group of soldiers or other military personnel assigned to protect the rear of a retreating or advancing force.
2. A defensive or protective position or measure taken at the rear of a military formation.
3. A person or group responsible for providing protection or support for a person or cause, especially in retreat or withdrawal.

Origin:

Mid 16th century: from rear + guard.

Examples:

1. The rearguard held off the enemy pursuit while the main army retreated to safety.
2. The rearguard action allowed the rest of the division to escape encirclement.
3. The rearguard was heavily armed and prepared for a last stand if necessary.
4. The rearguard provided cover for the retreat of the civilians from the war zone.
5. The rearguard was tasked with providing support and assistance to the advancing troops.