The translator of The Three Musketeers uses this in a way I believe is incorrect.
"As to Athos, he went out without any mystery, took his horse, which was tied with those of his friends to the fastenings of the shutters, in four words convinced the attendant of the necessity of a vanguard for their return, carefully examined the priming of his pistols, drew his sword, and took, like a forlorn hope, the road to the camp.




forlorn hope

NOUN: 1. An arduous or nearly hopeless undertaking. 2. An advance guard of troops sent on a hazardous mission.
ETYMOLOGY: By folk etymology from Dutch verloren hoop, advance guard : verloren, past participle of verliezen, to lose; see leu- in Appendix I + hoop, troop.