Infantry Drills

F-128: Machine Gun as a Base of Fire

Previous: F-127: Machine Guns in the Offense

F-128. Machine gun fire from a support-by-fire position must be the minimum possible to keep the enemy from returning fire. Ammunition must be conserved so the guns do not run out of ammunition.

F-129. The weapons squad leader positions and controls the fires of all medium machine guns in the element. Machine gun targets include essential enemy weapons or groups of enemy targets either on the objective or attempting to reinforce or counterattack. In terms of engagement ranges, medium machine guns in the base-of-fire element may find themselves firing at targets within a range of 800 meters. The nature of the terrain, desire to achieve some standoff, and METT-TC prompts the leader to the correct tactical positioning of the base-of-fire element.

F-130. The medium machine gun delivers an accurate, high-volume rate of lethal fire on fairly large areas in a brief time. When accurately placed on the enemy position, medium machine gun fires secure the essential element of fire superiority for duration of the firing. Troops advancing in the attack should take full advantage of this period to maneuver to a favorable position from where they can facilitate the last push against the enemy. In addition to creating enemy casualties, medium machine gun fire destroys the enemy’s confidence and neutralizes his ability to engage the friendly maneuver element.

F-131. There are distinct phases of rates of fire employed by the base-of-fire element:

  • Initial heavy volume (rapid rate) to gain fire superiority.
  • Slower rate to conserve ammunition (sustained rate) while still preventing return fire as the assault moves forward.
  • Increased rate as the assault nears the objective.
  • Lift and shift to targets of opportunity.

F-132. All vocal commands from the leaders to change the rates of fire are accompanied simultaneously by arm-and-hand signals.

F-133. Machine guns in the support by fire role should be set in and assigned a primary and alternate sector of fire as well as a primary and alternate position.

F-134. Machine guns are suppressive fire weapons used to suppress known and suspected enemy positions. Therefore, gunners cannot be allowed to empty all their ammunition into one bunker simply because it’s all they can identify at the time.

F-135. The support-by-fire position, not the assault element, is responsible for ensuring there is no masking of fires. The assault element might have to mask the support-by-fire line because it has no choice on how to move. It is the support-by-fire gunner’s job to shift fires continually, or move gun teams or the weapons squad to support the assault and prevent masking.

F-136. Shift and shut down the weapon squad gun teams one at a time, not all at once. M203/M320 and mortar or other indirect fire can be used to suppress while the medium machine guns are moved to where they can fire.

F-137. Leaders must take into account the surface danger zones of the machine guns when planning and executing the lift and or shift of the support-by-fire guns. The effectiveness of the enemy on the objective will play a large role in how much risk should be taken with respect to the lifting or shifting of fires.

F-138. Once the support-by-fire line is masked by the assault element, fires are shifted and or lifted to prevent enemy withdrawal or reinforcement.

Next: F-139: Machine Gun with the Maneuver Element

Go Back To: U.S. Army FM 3-21.8: The Infantry Rifle Platoon and Squad