What is the first action cadets take upon the command to 'open ranks, march'?

Upon receiving the command to 'open ranks, march,' the first action cadets take is to step back. This command instructs the formation to increase the distance between the individuals, thereby creating more space within the ranks. Each cadet takes a specified number of steps backward to facilitate this opening of ranks.

Understanding the purpose of this command is essential in military drilling, as it allows for better spacing and organization, ensuring that the formation looks uniform and can be maneuvered more efficiently. The subsequent actions following the initial step back would include adjustments to maintain alignment and cohesion as cadets respond to the command. The other options do not pertain to the immediate action required with the command, as they involve different formations or actions that are not executed at the moment of 'open ranks, march.'