Zhang Yi promised 600 li of land — he delivered six

In 314 BCE the Qin prime minister Zhang Yi arrived at the court of King Huai of Chu with an offer. If Chu broke its alliance with Qi, Qin would return 600 li of the Shangyu region it had conquered from Chu. The king was delighted. His senior advisor Chen Zhen alone counselled against it: 'Qin values Chu because Chu has Qi as an ally. If we break with Qi, Chu stands alone. Why would Qin give land to an isolated state? Zhang Yi will betray you.' King Huai refused to hear more: 'Keep your mouth shut and wait for the land.'

Zhang Yi returned to Qin and feigned a chariot injury, avoiding the Chu envoy for three months. By the time he reappeared, Qin had sealed its own alliance with Qi. Zhang Yi told the Chu envoy: 'I have a fief of six li. I am willing to give it to your king.' The envoy protested — the agreement was for 600 li, not six. Zhang Yi held firm. King Huai of Chu, enraged, launched an attack on Qin despite Chen Zhen's renewed pleas to negotiate instead.

The Chu army was crushed at Danyang by the combined forces of Qin and Qi, losing 80,000 men and the general Qu Gai. A second campaign at Lantian also failed. Chu lost the Hanzhong region and ceded another 600 li to Qin. King Huai had thrown away an alliance, a territory, and the strongest army in the south for a promise that was never real.