A great general is preparing for battle. He knows his enemy. His formidable opposite number on the other side will adopt one of three strategies. He must be prepared to counter any one of them.
He therefore prepares three grand plans, one for each of the three possible strategies his enemy may adopt in the forthcoming battle. He calls them Plan A, Plan B and Plan C. In the months before the battle messengers shuttle back and forth. They are carrying piece by piece the immense detail of each plan.
Then, when his enemy strikes, the general decides which plan is he must execute in order to defeat his enemy. He sends a simple abrupt message to all his company commanders. It simply reads: "Plan B". The message is very short. But it conveys an immense amount of information on how the battle should be fought.