Sun Wu, known to history as Sun Zi, was a great military strategist of the 5th century BC in China. He was considered "Father of Wars". His work The Art of War is also recognized as one of the most influential military books in China and worldwide. 
 
Born in 551 BC in the State of Qi, Sun Wu traveled to the State of Wu in the lower Yangtze valley at the age of 19. He stayed there to write his military books. His book The Art of War has brought him to the notice of the King of Wu, whose name goes by He Lu.  The King summoned him: " I've read all of your thirteen articles on military strategy and tactics" said the king, "and I want see whether they work in actual wars."
 
He asked Sun Wu to drill an army made up of his concubines, which Sun Wu agreed. He divided the 180 girls into two companies, and appointed one of the King's favorite concubines as the head of each company. He then explained to them the words of command.  
 
The drill then began. The two companies of girls burst into a hustle of laughter to the sound of drums. Sun Wu gave the words of command once again but they were still not obeyed. Sun Wu then ordered the leaders of the two companies to be beheaded. Now the king of Wu was stunned. He asked Sun Wu to spare them for he couldn't live on without them. But Sun Wu insisted beheaded the two leaders and  straightway installed the pair next in order as leaders in their place. When this had been done, the drum was sounded for the drill once more; and the girls went through all the evolutions, turning to the right or to the left, marching ahead or wheeling back, kneeling or standing, with perfect accuracy and precision, not venturing to utter a sound.   

After that, Ho Lu appointed Sun Wu as his general. The Wu army grew more powerful with Sun Wu as their head. In the years after, the Wu troops defeated the powerful State of Chu in the west and occupied its capital, thereafter threatening the states of Qi in what is now Shandong province and Jin to the northwest. In 482 BC, Wu became a dominant power in the area. 
 
After that, King He Lu grew ever more arrogant. Sun Wu refused great wealth and returned to the Luofu Mountains to live as a hermit, further polishing his book The Art of War.

The book, Sun Zi's Art of War, has become a classic down through the centuries. The principles he expounded are considered so relevant that they are studied today not only in China but in military academies around the world.