The Sichuan anti-Mongol fortresses are 83[1] mountain cities built by the soldiers and civilians of the
Southern Song Dynasty during the
Mongol conquest of China in
Sichuan to resist the invasion of the
Mongol Empire. Taking full advantage of the geographical advantages of the
Sichuan Basin,[2] these fortresses formed a comprehensive three-dimensional defense system, which succeeded in resisting the Mongol attacks for up to 53 years, greatly extending the life of Southern Song. They also made Sichuan the last to be conquered by the Mongolians in 1288.[1][3] Due to the defense of the fortresses, it was difficult to settle the Sichuan region. The Mongol Army had to abort its original strategy of "taking Shu (Sichuan) and destroying
Song" and moved to the area of
Jingzhou and
Xiangyang starting from 1271, defeating the Song Dynasty via the
Han River.[4]Möngke Khan became the only Mongol
khagan to perish on the battlefield when he died during an assault on Diaoyucheng in 1259.[5] He may have been a victim of
dysentery or of injuries sustained when attacking the fortress.[6]
The
Sino-Mongol wars in Sichuan began in 1227, known as the 1227 incident or the Dinghai incident. The Mongolian army attacked
Western Xia while sending troops into Sichuan, and captured five prefectures belonging to
Lizhou Circuit near Sichuan.[8] In 1236,
Kashin, the second son of
Ögedei Khan, led the Mongolian army to the south of Sichuan, breaking through the Song defense line at Kaizhou, Lizhou Circuit, and entered the
Sichuan Basin. Three circuits in Sichuan were almost completely occupied except
Kuizhou Circuit, and the Song only kept a few states such as
Luzhou,
Guo prefecture, and
Hezhou.[9] After this, the Mongolian army continued to invade Sichuan. In 1241, it took
Chengdu again, nearing
Kuizhou, and the Sichuan defense line was nearly destroyed. In 1241, Yu Jie moved the military and political center of Sichuan from Chengdu to Chongqing, which was easier to defend. After understanding that defending on flat land failed to stop the Mongol army, Yu began to build a mountain defense system and relocated the state government offices in the Sichuan province into the
Daba Mountains.[4] Most of the fortresses were located near cliffs of the mountains. The top of the mountains were wide and flat, there was enough
arable land and water, so they were self-sufficient and could be defended for a long time. At the same time, the mountain cities were often connected by rivers and roads at the junction of valleys or rivers. The defense of the Southern Song Dynasty used
Chongqing,
Jiading and
Kuimen as the centers of the defense of Sichuan, which resisted the invasion of Mongolia for 53 years. Even after the
Battle of Yamen in 1279, which ended the
Southern Song dynasty, two of the fortresses (Santaicheng and Lingxiaocheng) had not fallen. The former lasted for an extra year until 1280, and the latter lasted until 1288, making it the last place under Song control.[10]