What is the command given to have the unit take a step back while in formation?

The command "Back, March" is correctly used to instruct a unit to take a step back while in formation. This command serves a specific purpose in military drills, allowing troops to move in a cohesive manner while maintaining the integrity of their formation. The term "Back" specifies the direction of the movement, and "March" indicates the action to be taken.

In contrast, other commands do not initiate the same action or movement. "Step Back" lacks the formal structure typically associated with military commands, which may lead to confusion. The command "Halt" is used to stop the movement of personnel, without any backward action. Lastly, "Take Interval" is aimed at spreading out personnel within a formation rather than stepping back, thereby reinforcing the unique function of "Back, March" as the appropriate command for retreating in formation.