During the Warring States period, seven powerful states vied for supremacy, with Qin being the strongest. Intimidated by Qin's might, the other states scrambled for allies, employing either "vertical alliance" or "horizontal alliance" strategies. To divide and conquer the six rival states, Qin sent the strategist Zhang Yi to lobby them. Zhang Yi arrived in the state of Wei and persuaded King Wei to submit to Qin.
Zhang Yi met with King Xiang of Wei, analyzing the geopolitical landscape and Wei's precarious position.
Zhang Yi said to the King of Wei:
Wei was a small state, barely a thousand li across with only 300,000 soldiers, its flat terrain open to all directions like spokes on a hub. "Wei is only a hundred li from Han, and just over two hundred from Chu," the strategist explained, "with no mountains or rivers to block an enemy, they can march straight in. Surrounded by Chu to the south, Han to the west, Zhao to the north, and Qi to the east, guarding every border is impossible. If we aid Chu, Qi attacks from the east; if we help Qi, Zhao strikes from the north; if we don't ally with Han, they invade from the west; if we slight Chu, they come from the south. It's like Wei is being torn into four pieces."
“Therefore, the path of uniting other states against Qin is doomed to fail,” the strategist argued. “If Qin attacks Wei’s Yangjin, Zhao will lose contact with the southern states, and Wei will be cut off from the north—severing the alliance’s lifeline. Once that road is blocked, Wei cannot rest easy. Worse still, if Qin coerces Han into attacking Wei, the two powers will merge, and Wei’s fall will be imminent. For Wei’s own good, it is wiser to ally with Qin and seek its protection. If Wei joins Qin, Chu and Han will not dare to act rashly. Eliminating the threat from Chu and Han, Wei will have no worries from behind.”
"Furthermore, of all the states Qin seeks to weaken, none is more so than Chu, and none can weaken Chu more than Wei. Chu appears strong but is hollow at its core; with Wei's strength, victory is certain," the advisor urged. "So why not ally with Qin, weaken other states, and secure Wei's kingdom? Please make your decision swiftly."
After hearing Zhang Yi's analysis, King Wei found it sound, abandoned his original plan, and prepared to submit to the Qin state.
"The idiom 'split four ways and five apart' later came to describe something incomplete, disunified, decentralized, disunited, and completely fragmented."
Source: *Strategies of the Warring States*, Chapter "Strategies of Wei I"
Meaning of the Idiom: Later, the Chinese idiom "四分五裂" came to describe how something incomplete, disunified, decentralized, disunited, and completely fragmented.