in military usage, a long, narrow ditch with a one- or two-sided parapet, forming a fire position for motorized infantry subunits. Fire trenches also offer protection from enemy fire and tanks and permit concealed maneuvering.

Fire trenches are dug to a maximum depth of 2 m. For protection from enfilade fire, they are dug in zigzag or winding lines; the front and rear slopes have rifle pits, machine-gun emplacements, trench shelters beneath the parapet, and recesses. Some trench sections are covered. The slopes of fire trenches dug in soft soil are reinforced with poles, boards, and other materials.

From the 15th to 19th centuries, fire trenches were earth ditches, or parallels, used as a cover for troops preparing to attack a fortress: parallel trenches enabled the besieging army to advance by stages. Fire trenches in the modern sense were widely used in World War I after the front lines had come to a standstill and in World War II. Each defensive position included several lines of main trenches connected by communication trenches. Fire trenches were dug by hand or by trench diggers.