English Soldier,Military Historian and Inter-War Theorist
The principles of war, not merely one principle, can be condensed into a single word - "Concentration." But the truth this needs to be amplified as the concentration of strength against weakness. And for real value, it needs to be explained that the concentration of strength against weakness depends on the dispersion of your opponent's strength.
Be very careful never to show your own bias to anyone who is giving you information, or passing it on to you. Once he sees that you have a particular inclination he will instinctively tend to tell you what he thinks will suit you, and enhance your opinion of him.