“A weary, exhausted, nerve-racked group of men at noon, on November 1, assembled north of Sommerance, France to rest and dig in for the night. The artillery was still firing furiously, but the enemy’s bombardment had ceased suddenly about 10:00 am and now only occasional shells from long-range rifles would explode in the vicinity. The weather was gloomy and moist air chilled one to the bone. Yet it was with that methodical care that is characteristic of worn-out men that we prepared our foxholes, carrying boards and iron sheeting from abandoned machine- gunners dugouts in order to make our houses as comfortable as possible, even though only for one night. “- William L. Langer, Gas and Flame in WWI What type of warfare is described in the passage above?