公元前628年冬,秦国在郑国的间谍突然派人回国,向秦穆公报告:“郑国人信任我,把都城北门的钥匙交我保管,这是我国用兵的大好机会。如果您派一支军队袭击郑国,我们里应外合,一定可以占领郑国,借此扩大疆土,建功立业。”秦穆公喜出望外,决定调动大军,袭击郑国。作战经验丰富的老 In the winter of 628 BC, when the spies of the Qin state in Zheng State suddenly sent people back to the country, they reported to Qin Mu Gong: “The Zheng people trust me and give me the keys to the north gate of the capital, which is a great opportunity for our military use. An army attack on Zheng, we should be together, we must be able to occupy the Kingdom of Zheng, in order to expand the territory, meritorious service. ”Qin Mu Gong overjoyed, decided to mobilize the army, attacking Zheng. Combat experienced old