rearguard

/ˈɹɪəɹˌɡɑɹd/

ot noun

The rearmost part of a force, especially a detachment of troops that protect the rear of a retreating force.
The defence, collectively the defenders.

Manbalar: Wiktionary (Free Dictionary API orqali), Datamuse, Tatoeba (CC BY 2.0 FR), MyMemory.