The only surviving source on the life of Sun Tzu is a biography written in the 2nd century BCE by the historian Sima Qian. According to Qian, Sun Tzu was general who served in the state of Wu in the 6th century BC. He was a contemporary of  Confucius. According to tradition, Sun Tzu was a member of the landless Chinese aristocracy, the shi, descendants of nobility who had lost their dukedoms during the consolidation of the Spring and Autumn Period. Unlike most shi, who were traveling academics, Sun Tzu worked as a mercenary.
According to Qian, King Helu of Wu hired Sun Tzu as a mercenary general in 512 BCE after finishing his military treatise, The Art of War. Wu was considered a semi-barbaric state, that went on to become the most powerful state of the period by conquering Chu, one of the most powerful states in the Spring and Autumn Period. Sun Tzu disappeared after King Helu finally conquered Chu and the date of his death remains unknown.
Around 298 BCE, the historian Zhuang Zi, writing in the state of Zhao, recorded that Sun Tzu’s theories had been incorporated into the martial training techniques of both offensive and defensive tactics of the army.   
In 1972 a set of bamboo engraved texts were discovered in a grave near Linyi in Shandong. This version of The Art of War version was dated to between 134–118 BCE, and so ruled out theories that parts of the text had been written much later.
The Art of War remained one of the most popular works on war tactics and military strategy. The Chinese have long regarded the book as one of the most important works of Chinese literature.
Versions of The Art of War reached Europe shortly before the French Revolution in the form of a translation by a French Jesuit priest. It is believed Napoleon was a devotee of the texts. In the various translations, Sun Tzu is sometimes referred to as Sun Wu, and Sun Tzi. The works became staples of military teaching across Europe.
A resurgence of interest in the book happened in the United States in the 1970s after Henry Kissinger made reference to it. Versions of the book have also been released detailing the application of the principles to business, sports, diplomacy and personal development.

The Art of War

In the Art of War, warfare is above all a question of psychology and preparation. Long before actual battlefield strategy and tactics come into play a battle is potentially won or lost.
Perhaps his most important innovation in the strategy of warfare is the importance of intelligence and spying. While the techniques of intelligence gathering have changed greatly the importance of basing tactical decisions on reliable and up-to-date intelligence is still important today. His strategy is based on foreknowledge in order to know the strength and weaknesses (political, geographical, defensive, offensive) of your enemy. And if you are not strong enough, you should be cleverer through diplomacy.
It is also of importance to deceive your opponent to render his intelligence useless. According to Sun Tzu the art of war is the art of deception. “Apparent confusion is a product of good order; apparent cowardice, of courage; apparent weakness, of strength.”
Sun Tzu is a master of psychological warfare. His tactics are flexibility, gaining the initiative and not fighting a protracted war. For Sun Tzu, the ultimate victory would be to subdue the enemy without fighting.