General Stanley McCrystal from the U.S. Joint Special Operations Task Force in [https://hbr.org/2015/08/what-companies-can-learn-from-military-teams HBR » What Companies Can Learn from Military Teams]:
I still believe in rehearsals, but I’ve learned they have a different value. When I joined the Army Rangers in 1985 we’d rehearse airfield seizure operations—we’d parachute in wearing night vision goggles, and take the field. It’s a pretty complex thing, and we’d do it over and over. We’d have contingencies in case things went wrong, but we were always trying to make things as foolproof as we could.
The longer we did it, the more I realized the value of rehearsal was not in trying to get this perfectly choreographed kabuki that would unfold as planned.
The value of rehearsal was to familiarize everybody with all the things that could happen, what the relationships are, and how you communicate. What you’re really doing is ”’building up the flexibility to adapt”’.
I’ve never been on an operation that went as planned.