After six years’ of careful preparation， the national power of the Wu State had been greatly strengthened and it was now in a position to go to war against the Chu. Sun Tzu and Wu Zixu together formulated a plan to “exhaust and mislead the Chu.” The morale of the powerful Chu and its will to resist were gradually undermined and eroded by the Wu force’s frequent attacks. At the same time， many Chu allies defected to the Wu side， so that on the eve of war the Wu State effectively controlled the Yuzhang area of the Yangtze River and Huaihe River Valleys which lay between the Wu and Chu States. This would be vital in the coming conflagration.
Sun Tzu’s tactics centred around the need to deceive， mislead and above all exhaust the Chu forces. A policy of “Three against One” was adopted， whereby three forces would take turns attacking the enemy who effectively faced a fresh army each time. The army of the Chu State inevitably became exhausted and dispirited.
In the winter of 506 BC， King He Lü personally led an expedition with Sun Tzu and Wu Zixu as his generals. Allied with the States of Tang and Cai， total forces assembled on the Wu side numbered some 30，000. Turning from devious to direct tactics， they launched a surprise strategic attack on defences in the north of the Chu State. Under the command of Sun Tzu， the forces of the State of Wu advanced steadily beyond the Huaihe River and began the large-scale destruction of the Chu State in the greatest battles seen in the Chinese lands since the Shang and Zhou Dynasties (16th century BC-256 BC). Sun observed that there was nothing more difficult than tactical manoeuvres， which must be carried out in order to turn from devious to direct tactics.
In 1021 BC， or 500 years before the time of Sun Tzu， Jiang Taigong， a founding father of the State of Qi where Sun Tzu’s hometown was located， led an army against the King of Zhou. After crossing the Yellow River， they scuttled all available ferries. Later， this army who had cut themselves off from possible retreat， overthrew the Yin and Shang Empires. As Sun Tzu wrote in The Art of War： The general must sometimes place his soldiers in danger in order to make them move forward and not withdraw. However， SunTzu’s forces didn’t destroy the ferries after crossing the Huaihe River and coming ashore at Huangchuan， in Henan Province. Perhaps King He Lü insisted that the possibility of retreat be countenanced and didn’t allow it.
After a long march from Suzhou City， the armies of the State of Wu arrived at the banks of the Han River. The river was all that separated them from the capital of the Chu State. The unprepared Chu forces rushed out to confront the Wu armies.
This famous battle which took place 2，500 years ago， can be seen as almost certainly the first quasi-naval military engagement， despite the fact that it took place on a river and not at sea. King He Lü， Wu Zixu and Sun Tzu led a great force of soldiers from Taihu Lake， up the Yangtze River， north along the Huaihe River until eventually arriving in the Chu lands.
