If two men ride on a horse, one must ride behind

There cannot be two leaders in any enterprise. The man riding behind must leave it to the man in front to guide the horse. Similarly, on a tandem the man in front steers the machine and applies the brakes.

See also:

• Don't speak to the man at the wheel
• He that cannot obey cannot command
• It needs more skill than I can tell to play the second fiddle well
• Through obedience learn to command