No plan of operations extends with any certainty beyond the first contact with the main hostile force. - Field Marshal Helmuth Karl Bernhard Graf von Moltke (26 October 1800 – 24 April 1891)
Eisenhower co-opted this quote in Plans are worthless Plans are Everything.
So when you hear some say we don't need a Plan, we're Agile, ask yourself, what's the next step when something goes wrong