Dear anchita: I think it is a difference in scale. A vanguard is an appreciable portion of the army advancing, to prevent successful ambush. The story I was reading was about a relatively small cavalry unit, and just three men were the "vedettes". apparently sent ahead to detect any enemy cavalry unit capable of attacking while the squadron ws in terrain where they could not maneuver. Unfortunately I got a "Page not found" and so was able to read only one page. Now satellites and drone borne TV cameras are the
vedettes. Bill