What action signals the command to commence firing?

The action that signals the command to commence firing is extending the arm in front of the body and moving it in a horizontal arc. This gesture is a widely recognized form of non-verbal communication used in military operations to initiate action without the need for vocal commands, which is particularly important in situations where stealth is necessary or when noise could compromise the mission.

By moving the arm in a horizontal arc, it clearly indicates to team members that they should begin firing. This signaling method creates a visual cue that is easily discerned by others in a high-stress environment where sound may be masked or when the team is not in direct sight of the leader. It enhances coordination and maintains operational effectiveness by ensuring that all team members are aligned in their response to the command.

The other options do not serve the same purpose in a tactical context. For instance, raising both hands high above the head might suggest a different intention, possibly indicating a need for attention or a halt. Pointing the muzzle toward the ground could imply a temporary ceasefire, while squatting down and gesturing with hands lacks the clarity and decisiveness needed to communicate the order to commence firing effectively.