The Art of War is a Chinese military treatise that was written by Sun Tzu in the 6th century BC, during the Spring and Autumn period. Composed of 13 chapters, each of which is devoted to one aspect of warfare, it has long been praised as the definitive work on military strategies and tactics of its time, and one of the basic texts on the subject. The Art of War is one of the oldest and most successful books on military strategy in the world. It has had a huge influence on Eastern military thinking, business tactics, and beyond. Sun Tzu recognized the importance of positioning in strategy and that position is affected both by objective conditions in the physical environment and the subjective opinions of competitive actors in that environment. He taught that strategy was not planning in the sense of working through a to-do list, but rather that it requires quick and appropriate responses to changing conditions. Planning works in a controlled environment, but in a competitive environment, competing plans collide, creating unexpected situations.