What is the command to begin an extended rectangular formation?

The command "Extend to the left, march" is the correct command to initiate an extended rectangular formation. This command instructs the soldiers to extend their formation laterally, moving to the left in a synchronized manner, which is crucial for creating the specified formation.

In military drill and ceremonies, initiating formations involves precise and clear commands that ensure units understand their movements and align properly. "Extend to the left, march" ensures that soldiers know to spread out and position themselves in a rectangular or expanded formation, maintaining proper spacing and alignment.

The other commands provided do not serve this specific purpose. For instance, "Right, Face" simply instructs soldiers to pivot to the right while standing and does not facilitate the formation needed for an extended rectangle. "Even numbers to the right, uncover" relates to organizing troops for visibility but is not a command for forming the extended rectangle. Similarly, "Count off from right to left" pertains more to organizing personnel rather than forming a designated formation. Thus, the command to extend towards the left is essential for achieving the intended layout of soldiers in this specific maneuver.