What command can be issued by anyone on the firing line?

The command "Cease fire" is universally recognized as a critical safety directive that can be issued by anyone on the firing line. Its primary purpose is to immediately stop all shooting and to ensure the safety of all personnel present. This command is vital in preventing potential accidents or misfires and is a necessary measure to maintain safety during training or operational scenarios.

In contrast, the other commands typically have specific contexts or are designated for use by authorized personnel only. "Fire at will" or "Ready, aim, fire" generally imply a level of authority over the firing process, often reserved for range officers or instructors. "Stand down" is usually utilized to indicate a reduction in readiness levels or a return to normal operations but might not be appropriate for immediate safety concerns like "Cease fire."