Sun Wu, better known as Sun Tzu or Sunzi, was an ancient Chinese military general, strategist and philosopher who is traditionally believed, and who is most likely, to have authored The Art of War, an influential ancient Chinese book on military strategy. Sun Tzu has had a significant impact on Chinese and Asian history and culture, both as an author of The Art of War and through legend. During the 19th and 20th centuries, Sun Tzu's The Art of War grew in popularity and saw practical use in Western society, and his work has continued to influence both Asian and Western culture and politics.
Historians have questioned whether or not Sun Tzu was an authentic historical figure. Traditional accounts place him in the Spring and Autumn Period of China (722–481 BC) as a military general serving under King Helü of Wu, who lived c. 544—496 BC. Modern scholars accepting his historicity place the completion of The Art of War in the Warring States Period (476–221 BC), based on the descriptions of warfare in the text, and on the similarity of text's prose to other works completed in the early Warring States period.
The Art of War is one of the oldest and most successful books on military strategy in the world. It has been the most famous and influential of China's Seven Military Classics: "for the last two thousand years it remained the most important military treatise in Asia, where even the common people knew it by name." It has had an influence on Eastern military thinking, business tactics, and beyond.
Sun Tzu emphasized the importance of positioning in military strategy, and that the decision to position an army must be based on both objective conditions in the physical environment and the subjective beliefs of other, competitive actors in that environment. He thought that strategy was not planning in the sense of working through an established list, but rather that it requires quick and appropriate responses to changing conditions. Planning works in a controlled environment, but in a changing environment, competing plans collide, creating unexpected situations.
Source: Wikipedia, "Sun Tzu", available under the CC-BY-SA License.