Write an article that answers the following question: How many years after Qin Hui was promoted, did the Battle of Yancheng occur?
Gaozong promoted Qin Hui in 1138 and put him in charge of deliberations with the Jin. Yue Fei, Han Shizhong, and a large number of officials at court criticized the peace overtures. Aided by his control of the Censorate, Qin purged his enemies and continued negotiations. In 1138 the Jin and Song agreed to a treaty that designated the Yellow River as border between the two states and recognized Gaozong as a "subject" of the Jin. But because there remained opposition to the treaty in both the courts of the Jin and Song, the treaty never came into effect. A Jurchen army led by Wuzhu invaded in early 1140. The Song counteroffensive that followed achieved large territorial gains. Song general Liu Qi  won a battle against Wuzhu at Shunchang . Yue Fei was assigned to head the Song forces defending the Huainan region. Instead of advancing to Huainan, however, Wuzhu retreated to Kaifeng and Yue's army followed him into Jin territory, disobeying an order by Gaozong that forbade Yue from going on the offensive. Yue captured Zhengzhou and sent soldiers across the Yellow River to stir up a peasant rebellion against the Jin. On July 8, 1140, at the Battle of Yancheng, Wuzhu launched a surprise attack on Song forces with an army of 100,000 infantry and 15,000 horsemen. Yue Fei directed his cavalry to attack the Jurchen soldiers and won a decisive victory. He continued on to Henan, where he recaptured Zhengzhou and Luoyang. Later in 1140, Yue was forced to withdraw after the emperor ordered him to return to the Song court.