Infantry In Battle
It contained a number of case studies from the Great War, used to illustrate a number of infantry concepts (obscurity, simplicity, terrain, time/space, mobility, surprise, orders, command/communication, fire/movement, artillery, etc). The case studies are morbidly fascinating... In each example, anywhere between tens to thousands of men slogged it out in the fields of Europe, often loosing their lives due to bad information, shaky leadership, or sheer chance. There have been a number of movies that depict the trench warfare of WWI (dark skies, muddy trenches, another wave of men getting cut down by in a hopeless charge at machine guns), and this is a good complement to understand why those things were happening (on a tactical level).
It follows, then, that the leader who would become a competent tactician must first close his mind to the alluring formulae that well-meaning people offer in the name of victory. To master his difficult art he must learn to cut to the heart of a situation, recognize its decisive elements and base his course of action on these. The ability to do this is not God-given, nor can it be acquired overnight; it is a process of years. He must realize that training in solving problems of all types, long practice in making clear, unequivocal decisions, the habit of concentrating on the question at hand, and an elasticity of mind, are indispensable requisites for the successful practice of the art of war.