Chongqing - From July 13 to 15, the international symposium “Mutual Learning Among Civilizations: International Symposium on the Conservation and Utilization of the World Cultural Heritage Site of Xanadu and the Theory and Practice of Chinese Frontier Archaeology” was held in Xilingol League, Inner Mongolia. More than 120 archaeologists and historians from China, the United States, Russia, South Korea, Mongolia, and other countries gathered on the Jinlianchuan Grassland to explore the civilizational codes of grassland capitals and to discuss pathways for building an independent knowledge system in archaeology.
Yuan Dongshan, a researcher at the Chongqing Institute of Cultural Relics and Archaeology and the lead archaeologist at the Diaoyu Fortress site, delivered a keynote speech that unveiled the true historical significance of the archaeological excavations at Hechuan Diaoyu Fortress (Diaoyucheng). He argued that this protracted siege warfare forced Kublai Khan to shift from military conquest to Sinicized governance, objectively heralding a new chapter of large-scale ethnic integration in Chinese history.
Yuan Dongshan is delivering a keynote speech at the symposium. (Photo provided by the interviewee)
Gunpowder, Thunderbolts, and Tunnels: “Black Tech” Forged in the Crucible of War
In July 2025, startling news came from the Jiadantu archaeological site at Diaoyu Fortress: laboratory tests conducted by Chongqing University revealed that the rammed-earth platform built by Southern Song defenders reached a compressive strength of 10 megapascals—far exceeding the normal 1-megapascal limit of ordinary clay rammed earth and approaching that of conventional cement. The discovery amazed archaeologists and geotechnical engineers on site.
The Hechuan Diaoyu Fortress archaeological site in Chongqing. (Photo provided by the interviewee)
It turned out that Southern Song craftsmen had mastered a “black technology”: they first rammed a base layer of fine clay mixed with small sandstone fragments, then covered it with irregular stones weighing dozens of jin (catties), and finally sealed the surface with a specially formulated fine mud. This three-layer structure enhanced waterproofing and shock absorption while rapidly raising elevation, maximizing the defenders’ firepower advantage.
Such ingenuity can be seen everywhere in the fortress. At the Fanjiayan site west of the city, archaeologists unearthed a sophisticated drainage system with open and covered channels and reservoirs. More than a dozen sky ponds atop the mountain and 92 water wells ensured that the garrison “never went thirsty.” Excavations also revealed granaries large enough to store five years’ worth of grain—all part of a fortress tailor-made for protracted warfare, “never to be conquered.”
Even more striking were the discoveries of firearm relics. During excavations of a more-than-100-meter-long Mongol tunnel near Qisheng Gate and the southern naval dock, multiple fragments of iron thunderbolts were recovered. According to Yuan Dongshan, these are among the world’s earliest known examples of explosive firearms. Similar iron thunderbolts—more than 80 in total—were found in the site’s tunnels.
After the Gates Opened: Seeds of Civilizational Blending Take Root
In 1279, Wang Li, the last defender of Diaoyu Fortress, made a decision that shocked the realm: he surrendered the fortress. But it was not an unconditional capitulation—it came with a demand: no massacre of the city’s inhabitants.
Kublai Khan kept his word.
The “tough nut” that had withstood Mongol cavalry for nearly 40 years finally fulfilled its historical mission through peaceful means. The war banners atop the walls were lowered, but the city’s people survived. Its culture endured, and the seeds of civilizational exchange took root in the blood-soaked soil.
After the war ended, the eastern Sichuan region, where Hechuan Diaoyu Fortress is located, underwent a slow yet profound process of integration, Yuan said.
After establishing the Yuan dynasty, Kublai Khan deeply reflected on the lessons of Diaoyu Fortress. The mountain-city defense system built among the mountains and rivers of Bashu had successfully blocked Mongol cavalry for decades, making him realize that military force alone could not secure lasting rule over the Central Plains. He sought a path forward through institutions and culture, promoting Han-style laws, welcoming Central Plains scholars and elites, and establishing a governance system that balanced nomadic traditions with agrarian civilization.
In this sense, the Diaoyu Fortress's determined resistance objectively imposed a significant cost on the Mongol forces, buying them time to understand and eventually embrace the civilization they had conquered.
Integration was not limited to the political sphere; it also permeated the daily lives of ordinary people. After the Yuan unification, the fate of former Southern Song garrison soldiers was telling: some laid down their arms and returned to farming, becoming part of local communities; others joined the Yuan military and administrative systems and continued their service.
Historical records show that local residents resumed farming, trading, marriage, and celebrations as before. The divisions of wartime gradually gave way to shared daily life. Mongols and Han people lived side by side, their customs intermingled, and the former fortress transformed into a peaceful market town.
Meanwhile, similar stories unfolded in more than a hundred other Song-Mongol mountain cities across Sichuan. These strongholds, originally built as military defenses against external threats, eventually became places where different ethnic groups came into contact, coexisted, and integrated.
Yuan Dongshan said that the story of Diaoyu Fortress still carries significance today. Through one city’s life-or-death decision, it tells later generations that confrontation is not the end of history—integration is. In an era of frequent global civilizational tensions, the wisdom embodied by Diaoyu Fortress offers a reference point for bridging divides and pursuing coexistence among civilizations.
(Zhang Xuege, as an intern, also contributed to this article.)