OUTGUARD
Etymology
Noun
outguard (plural outguards)
(military) A guard or small body of troops at a distance from the main body of an army, to watch for the approach of an enemy.
(by extension) Anything for defense placed at a distance from the thing to be defended.
Source: Wiktionary
Out"guard`, n. (Mil.)
Definition: A guard or small body of troops at a distance from the main
body of an army, to watch for the approach of an enemy; hence,
anything for defense placed at a distance from the thing to be
defended.
Source: Webster’s Unabridged Dictionary 1913 Edition