Middle English reregardefrom Old French rerebackward (from Latin retrōre- in Indo-European roots) guardeguard (fromguarderto defendguard)
American Heritage Dictionary of the English Language, 5th Edition
Rear-guard Sentence Examples
Six hours earlier his conclusion would have been correct, but early that morning the Prussian headquarters, alarmed for the safety of their line of retreat on Berlin by the presence of the French in Naumburg, decided to leave Hohenlohe and Rachel to act as rear-guard, and with the main body to commence their retreat towards the river Unstrutt and the Eckhardtsberge where Massenbach had previously reconnoitred an " ideal " battlefield.
If confronted by a rear-guard he would drive it off and occupy Quatre Bras; and if Wellington was still there the marshal would promptly engage and hold fast the Anglo-Dutch army, and report to the emperor.
The retreat was admirably conducted; Lord George and Cluny fought a gallant and successful rear guard at Clifton; they escaped from Cumberland across the border, but Charles, against advice, left a doomed garrison in Carlisle.
The retreat was covered by the Vicenza battalion of Alpini, who fought a gallant rear-guard action, and a strong counter-attack by the group of Alpini from Marostica checked the Austrian pursuit.
This defeat of the rear-guard, famous for the death of the great Roland and the treachery of Ganelo, induced the Arabs to take the offensive once more and to conquer Septimania.