This period in Chinese history came after the Zhou and the Shang dynasties had existed side by side fairly amicably for a long time. Then the individual states became competitive and wars broke out between them.
It was no longer an enormous and stable country, China, but uncertain and disruptive for the people. The warring betweenn the states allowed another dynasty to begin so that control could be established over all these individual states. The Zhou dynasty took over then/ It was founded by King Wen of the Ji family in 1076 BC, after the Shang dynasty came to an end.
The warring states or Zhanguo or Chan-Kuo period came immediately before the Qin dynasty and was the reason or cause of that dynasty succeeding. There had been peaceful periods during the Zhou dynasty (the Spring and Autumn periods) but various states became unsettled and set war upon others during the period of 475 BCE until the establishment of the Qin dynasty in 221 BCE.
The period of the Warring States commenced when the numerous and small city-state kingdoms had been consolidated into seven major competitive ones, plus a few minor additions. The Qin dynasty, though short, was far more successful and permanently influential than the warring period.
However, the Zhou dynasty was itself highly significant and determining before the warring of the small states.