I was mindful of this recently when reading about Eisenhower this week and came across this quote:
"In preparing for battle, I have always found that plans are useless but planning is indispensable".
I believe that what he was saying here is that the act of planning, the communication itself, discussing the angles, raising the various possibilities for failure and options for avoiding them, is by far the most valuable aspect of the planning process. The resulting plan itself is actually of little worth because it is highly likely that you'll need to change the plan in response to an unforeseen challenge.
Our planning meetings have to be highly interactive events where the team is able to engage in good discussion covering how they are going to turn the backlog into real working software, not necessarily covering every story in great detail but definitely pulling together an idea of how they are going to get from A to B and raising as many risks they can think of. The result is a plan but more than that, each member of the team is equipped with valuable knowledge that allows them to stay in tune with the progress and alert to the effect any risks may be having on that plan so they can confidently react to any need for changing it as they go.
Of course the main planning meeting is not the end of it, the team needs the opportunity to regularly refocus, update and re-plan if necessary as they work their way through the iteration and as we know the daily stand up is precisely for that purpose. Fifteen minutes of concentrated planning in the form of an update on whats done and an agreement of whats next along with an acknowledgement of current risk.
It seems obvious to me that Eisenhower was absolutely right, it's not about the plan it's all about the planning.