The remains of Shang dynasty was only re-discovered in the 20th century, some 3000 plus years after the event.
Before that the history of Shang was largely presented by the Zhou, in order to show their legitimacy in overthrowing the Shang, they have propagandized that the Shang was no longer able to rule China.
Previously lack of archeaological evidence, but heavy influence by the Zhou presentation. Now with more objective study, King Zhou has his contribution in which he accelerated fusion between people of central plain and those of Dongyi, his campaigns led to territorial expansion into Shandong penninsula, lower reaches of Huai river, and the Yangtze river.
The Shang of late period was warlike, according to discovery at ruins of Yin/Shang in Henan province, their capital Chaoge had no defensive city walls, despite its being there for some 270 years. As introduced by discovery channel's documentary, the Shang army had big chariots, were equipped with bronze weaponry, for awhile, the Shang had no opponent.
Although, the Zhou dynasty lasted longer, their power declined gradually not long after re-establishment of Eastern Zhou, when it was finally diminished by the Qin, there was not much of its former Glory left, its power has shrinked greatly.
But the Shang was a different story, when its about to be replaced by the Zhou, the Shang under the leadership of King Zhou was at the height of its territorial expansion, contrary to the late Zhou central power which had little territory left for themselves.
The Shang was actually too powerful thus stretched itself too much. The Zhou army with only less than 1/8 of that of Shang army could easily defeat once the mighty Shang, who had no problem during King Zhou's previous military conquest in the south and east? As history recorded, the cause of Shang defeat was the slave army of Shang rebelled, they let the Zhou army pass without a fight, instead, many turned against the Shang.
Similar was with the battle of Feishui, when Fujian was defeated there, he actually just gained unification of northern China not long ago. With 830k vast army, he was defeated by Eastern Jin army which was 10 times smaller.
The major cause is that the Han-Chinese in his formation were not willing to fight, other nomads who also had their own ambitions, were not willing to die for former Qin as well. The Shang also had some 700k army, but was defeated by Zhou force of only 80,000 men, the Dongyi slave soldiers didnt want to fight for the Shang, since they were forced to participated in the battle in the first place.
Edited by The Charioteer - 29-Aug-2006 at 23:07