소진
After King Zhao of Yan (312–279 BC) ascended to the throne, the state suffered upheaval and bloodshed so the king, planning to strengthen his state and avenge former humiliation, summoned his sages. Su Qin immediately left Zhou and travelled to the Yan. For King Zhao of Yan, Su Qin carried out his first meritorious service by petitioning King Xuan of Qi to return the ten cities he had previously snatched. The Yan sent a prince as hostage to the Qi with Su Qin acting as envoy. This was in the seventh year of the reign of King Min of Qi, 294 BCE when the government of the Qi was presided over by Lord Mengchang. Su Qin was treated well in Qi and was on friendly terms with Lord Mengchang before his return to Yan.