The Song dynasty ended primarily due to military defeat and conquest by the Mongol-led Yuan dynasty. The dynasty initially suffered a major loss in 1127 when the Jurchen-led Jin dynasty invaded from the north, capturing key territories and forcing the Song court to retreat south, thereby dividing the dynasty into the Northern Song (960–1127) and Southern Song (1127–1279) periods. Despite efforts to defend its territory, the Song were weakened by internal political struggles, military disadvantages, and constant pressure from northern neighbors. In the 13th century, the Mongols under Kublai Khan began attacking Song territory after overthrowing the Jin dynasty. By 1273, the Mongols captured strategic cities and penetrated deep into Song lands. The decisive end came in 1279 at the Battle of Yamen, where the Mongol navy defeated the Song fleet. The last Song emperor reportedly drowned during this battle, marking the fall of the dynasty and the beginning of Mongol rule over all of China under the Yuan dynasty. In summary, the Song dynasty ended due to cumulative military defeats against northern invaders—the Jin and ultimately the Mongols—combined with internal weaknesses and political fragmentation, culminating in the Mongol conquest and naval defeat at Yamen in 1279.