There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don’t know. But there are also unknown unknowns. There are things we don’t know we don’t know.
A commander in chief cannot take as an excuse for his mistakes in warfare an order given by his minister or sovereign, when the person giving the order is absent from the field and is imperfectly aware of wholly unaware of the state of affairs.