To trench at

to make trenches against; to approach by trenches, as a town in besieging it.

See also: Trench

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
Trenching in difficult conditions is not new to Pruett, but the circumstances that led him to trench at night - with deer and bobcats stating into the aircraft-strength lights on his trenchers - were something he hadn't experienced before.
"We opted to trench at night so that we didn't shut the whole project down.