rearguard
noun /ˈrɪəɡɑːd/
/ˈrɪrɡɑːrd/
(usually the rearguard)
[singular + singular or plural verb]- a group of soldiers that protect the back part of an army especially when the army is retreating after it has been defeated opposite vanguardWord Originlate Middle English (denoting the rear part of an army): from Old French rereguarde.