Military Parade, North Korea

There is only one person in charge a parade at a time. Changing this person is very ceremonious. This is to make it obvious to the soldiers who is currently in command and therefore to whom to pay attention.
During parades, unless explicitly told otherwise, soldiers have restricted movement, meaning they can move only exactly when they are told, and then doing only exactly what they are told to do. In most stances, any movement at all is disallowed and is held to such an extent as to have soldiers fainting on parade, although fainting under any conditions short plural hours standing still in the hot sun is considered a sign medical disability.
American usage allows the service member to be at four states alert:
Attention: standing straight, eyes forward, chest out, knees straight but not locked, feet together at a 45-degree angle.