During the Eastern Zhou Dynasty, iron weapons appeared, and bronze weapons were gradually replaced. Since then, infantry and cavalry have been separated and divided into two arms, and the way of fighting has evolved.

Previously, the unitized phalanx of the "three divisions" became a diversified phalanx. The corps formed by each branch of the army began to use "three formations" or "five formations". The so-called "three formations" means that a team is divided into the left wing, the right wing, and the middle army, and the whole of the three parts may not be rectangular, but it still retains the characteristics of facing the enemy in a wide front.

Generally speaking, the Chinese army is the main force with the highest morale and the largest number of people in the whole army, and it plays the greatest role on the battlefield. Although the soldiers on both flanks are smaller, they must be the strongest in individual combat, and they will play a role in a war.

Over time, the "five" gradually replaced the "three".

This formation consisted of the vanguard of the road, the front army, the right army, which protected the military vehicles, the left army, which was responsible for the grain and grass baggage, the rear army, and the central army, which was mainly composed of military vehicles. Compared with the previous "Yuli Array", the function of this formation is more perfect. The "Jing Corpse Array" that the Chu people make good use of is a classic "Five Arrays".

There are many classic battles that use the "Five Formations", the most impressive is a war commanded by Wei Shu, a Jin doctor, in 541 BC. The opponents of the Jin army, the Di people, were very strong, and the two armies were in a cramped valley formation. Wei Shu boldly adopted the tactic of "destroying the chariot to act", using the infantry as the leading, giving up the efficiency of the chariot in exchange for mobility, so as to successfully win the war.

During the Warring States Period, Sun Bin of Qi pushed the development of formations to a climax, and the "Ten Formations" invented by him once influenced the future cold weapon war. The "Eight Formations" that Zhuge Liang was good at in the Three Kingdoms era was actually an improvement of Sun Bin's "Eight Formations".