TheSichuan anti-Mongol fortresses are 83[1] mountain cities built by the soldiers and civilians of theSouthern Song Dynasty during theMongol conquest of China inSichuan to resist the invasion of theMongol Empire. Taking full advantage of the geographical advantages of theSichuan 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 destroyingSong" and moved to the area ofJingzhou andXiangyang starting from 1271, defeating the Song Dynasty via theHan River.[4]Möngke Khan became the only Mongolkhagan to perish on the battlefield when he died during an assault on Diaoyucheng in 1259.[5] He may have been a victim ofdysentery or of injuries sustained when attacking the fortress.[6]
TheSino-Mongol wars in Sichuan began in 1227, known as the 1227 incident or the Dinghai incident. The Mongolian army attackedWestern Xia while sending troops into Sichuan, and captured five prefectures belonging toLizhou Circuit near Sichuan.[8] In 1236,Kashin, the second son ofÖgedei Khan, led the Mongolian army to the south of Sichuan, breaking through the Song defense line at Kaizhou, Lizhou Circuit, and entered theSichuan Basin. Three circuits in Sichuan were almost completely occupied exceptKuizhou Circuit, and the Song only kept a few states such asLuzhou,Guo prefecture, andHezhou.[9] After this, the Mongolian army continued to invade Sichuan. In 1241, it tookChengdu again, nearingKuizhou, 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 theDaba Mountains.[4] Most of the fortresses were located near cliffs of the mountains. The top of the mountains were wide and flat, there was enougharable 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 usedChongqing,Jiading andKuimen as the centers of the defense of Sichuan, which resisted the invasion of Mongolia for 53 years. Even after theBattle of Yamen in 1279, which ended theSouthern 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]
