Flank defense

(Fort.) protection of a work against undue exposure to an enemy's direct fire, by means of the fire from other works, sweeping the ground in its front.

See also: Flank

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
They were surrounded by higher ground held by the enemy, and each one depended on the others for flank defense. If one outpost fell, the others were as vulnerable as a stack of dominos in a hurricane.