"fire trenches" is a correct and usable phrase in written English.
It is used to describe a system of trenches dug to serve as a defense against enemy fire. For example: "The Army dug fire trenches around the base to protect against enemy attack."
They spent the next few days improving the fire trenches, constructing communications trenches, and enlarging tracks so men and guns could move forward quickly.
The trenches varied in depth, but they were usually about four or five feet deep, or in areas with a high water table a wall of sandbags would be built to allow the defenders to stand upright, fire trenches were provided with a fire step, so the occupants could return fire during an attack (see diagram).
Lance Corporal Hall came in a little later and urged them to come back out to the fire trench "to hear something that will take you home to Blighty". With some urging, Empey and two others joined him.
When we stopped and got off, he showed me where the fire trench had been; he pointed to the German line about 90 yards distant, still marked by the indestructible concrete pillboxes.
A risk assessment for "Eden," compiled in November, 2015, warned of the dangers of fire, trench foot, hypothermia, and "persons becoming aggressive and acting violent due to the stresses of living wild".
"It was a classic--absolutely classic--military breaching of a very, very tough minefield with barbed wire, fire trenches-type barrier," Schwarzkopf continued.
The Australians held the old Ottoman fire trench and had footholds deeper in Ottoman lines.
There were three trenches in a typical front line sector; the fire trench, the support trench and the reserve trench, all joined by communication trenches.
The "KSC Up-Close: Launch Pad Tour" will include visits to structures that supported and protected the space shuttle, water tanks that fed a noise suppression system, and the flame trench that deflected fire and smoke from the engines.
A fire break trench has been dug around the smouldering pile at Thoby Lane in Mountnessing near Brentwood.
The AU unit of about 100 troops, most of them Nigerian, fought off the first attack before falling back to trenches, firing through the night until their ammunition ran out.
