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In the sixth year of Duke Cheng of Lu (585 CE), the State of Jìn attacked the State of Cài. Chǔ sent troops from Shēn and Xī to assist Cài. The high-ranking military leaders of Jìn knew that if they won this battle it would only mean the defeat of Shēn and Xī counties, not the entire State of Chǔ – if they lost it would be a major humiliation so the army decided to retreat. Academic Gu Jiegang points out that since the two counties of Shēn and Xī had enough troops and were sufficiently powerful to deal with the State of Jin's army, it is clear that the counties were both rich and populous.