He Who Defends Everything Defends Nothing

Associated with Frederick's military instructions and often traced to his Instructions for His Generals (1747), this maxim encapsulates his principle of concentrated force. Frederick ruled Prussia — a small state surrounded by larger powers — and could never afford to hold every frontier equally. His campaigns in the Silesian Wars and the Seven Years' War were built on interior lines: concentrating troops rapidly to strike at exposed points rather than spreading thin across all fronts. The same principle was absorbed by Carl von Clausewitz, who served in the Prussian army during Frederick's era and incorporated it into On War.