The name Zhou appears often in the oracle bone inscriptions of the Shang kingdom, sometimes as a friendly tributary neighbor and at other times as a hostile one. This pattern is confirmed by records found at the Zhou archaeological site. Marriages were occasionally made between the two ruling houses. The Zhou also borrowed arts such as bronze casting from their more cultivated neighbor. The Zhou royal house, however, had already conceived the idea of replacing Shang as the master of China—a conquest that took three generations. Although the conquest was actually carried out by his sons, Wenwang should be credited with molding the Zhou kingdom into the most formidable power west of the Shang. Wenwang extended the Zhou sphere of influence to the north of the Shang kingdom and also made incursions to the south, thus paving the way for the final conquest by Wuwang.

In Chinese historical tradition Wenwang was depicted as intelligent and benevolent, a man of virtue who won popularity among his contemporaries and expanded the realm of the Zhou. His son Wuwang, though not as colorful as his father, was always regarded as the conqueror. In fact, Wu, his posthumous name, means “Martial.” However, the literary records indicate that the Zhou actually controlled two-thirds of all China at the time of Wenwang, who continued to recognize the cultural and political superiority of the Shang out of feudal loyalty. There is not enough evidence either to establish or to deny this. A careful historian, however, tends to take the Zhou subjugation to the Shang as a recognition of Shang strength. It was not until the reign of the last Shang ruler, Zhou, that the kingdom exhausted its strength by engaging in large-scale military campaigns against nomads to the north and against a group of Indigenous tribes to the east. At that time Wuwang organized the first probing expedition and reached the neighborhood of the Shang capital. A full-scale invasion soon followed. Along with forces of the Zhou, the army was made up of the Jiang, southern neighbors of the Zhou, and of eight allied tribes from the west. The Shang dispatched a large army to meet the invaders. The pro-Zhou records say that, after the Shang vanguard defected to join the Zhou, the entire army collapsed, and Wuwang entered the capital without resistance. Yet Mencius, the 4th-century-bce thinker, cast doubt on the reliability of this account by pointing out that a victory without enemy resistance should not have been accompanied by the heavy casualties mentioned in the classical document. One may speculate that the Shang vanguard consisted of remnants of the eastern tribes suppressed by the Shang ruler Zhou during his last expedition and that their sudden defection caught the Shang defenders by surprise, making them easy prey for the invading enemy. The decisive battle took place in 1111 bce (as tabulated by Dong Zuobin, although it is traditionally dated at 1122; other dates have also been suggested, including 1046, which has been adopted for this article). Wuwang died shortly after the conquest, leaving a huge territory to be consolidated. This was accomplished by one of his brothers, Zhougong, who served as regent during the reign of Wu’s son, Chengwang.

The defeated Shang could not be ruled out as a potential force, even though their ruler, Zhou, had immolated himself. Many groups of rival tribes were still outside the sphere of Zhou power. The Zhou leaders had to yield to reality by establishing a rather weak control over the conquered territory. The son of Zhou was allowed to organize a subservient state under the close watch of two other brothers of Wuwang, who were garrisoned in the immediate vicinity. Other leaders of the Zhou and their allies were assigned lands surrounding the old Shang domain. But no sooner had Zhougong assumed the role of regent than a large-scale rebellion broke out. His two brothers, entrusted with overseeing the activities of the son of Zhou, joined the Shang prince in rebellion, and it took Zhougong three full years to reconquer the Shang domain, subjugate the eastern tribes, and reestablish the suzerainty of the Zhou court.

These three years of extensive campaigning consolidated the rule of the Zhou over all of China. An eastern capital was constructed on the middle reach of the Huang He (Yellow River) as a stronghold to support the feudal lords in the east. Several states established by Zhou kinsmen and relatives were transferred farther east and northeast as the vanguard of expansion, including one established by the son of Zhougong. The total number of such feudal states mentioned in historical records and later accounts varies from 20 to 70; the figures in later records would naturally be higher, since enfeoffment might take place more than once. Each of these states included fortified cities. They were strung out along the valley of the Huang He between the old capital and the new eastern capital, reaching as far as the valleys of the Huai and Han rivers in the south and extending eastward to the Shandong Peninsula and the coastal area north of it. All these colonies mutually supported one another and were buttressed by the strength of the eastern capital, where the conquered Shang troops were kept, together with several divisions of the Zhou legions. Ancient bronze inscriptions make frequent mention of mobilizing the military units at the eastern capital at times when the Zhou feudal states needed assistance.