/ ˈrɪəgɑːd; NAmE ˈrɪrgɑːrd/ noun
(usually the rearguard ) [ sing.+ sing./pl. v . ] a group of soldiers that protect the back part of an army especially when the army is retreating after it has been defeated
OPP vanguard
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WORD ORIGIN
late Middle English (denoting the rear part of an army): from Old French rereguarde .