A series of Jurchen military campaigns against the Song Dynasty began with a declaration of war in November 1125. The Jurchen Jin Dynasty had previously allied with the Song against the Khitan Liao Dynasty, but invaded the Song after a series of failed negotiations. The cities of Taiyuan and the Song capital of Kaifeng were besieged by the Jurchens, who briefly retreated from Kaifeng after the Song agreed to pay a large annual indemnity. The Chinese emperor was captured during the second Jurchen siege of Kaifeng in 1127. A treaty in 1142 settled the boundary between the two empires, but conflicts ensued for the remainder of both dynasties.