[Why] The Mongol army in three columns launched grand encirclement against Song, with Great Khan Mongke personally leading the main force in a wild storm to besiege the strategic throat of Bashu. The Diaoyu City holding the confluence of the Yangtze and Jialing Rivers became the absolute mainstay of resistance. [What] Song general Wang Jian led military and civilians to grimly defend in the isolated Diaoyu City, relying on solid mountain-city works to repel the Mongol army's countless charges. Mongke Khan personally went to the front line to supervise the battle and was struck dead by a flying stone. [Who] Wang Jian was a wise and brave Southern Song Sichuan-Shu city-defense master who deeply won popular support. Mongke Khan was the Mongol Empire's south-and-north-campaigning unmatched valiant great khan, and his accidental death wholly broke the empire's expansion process. [How] Mongke's death directly forced the Mongol iron cavalry fighting in Europe and the Middle East to wholly withdraw to fight for the throne, successfully changing the overall direction of world history. It became the most glorious defensive epic in world military history.
Why
The historic event of Siege of Diaoyu Fortress represents a key developmental peak of the Huaxia dynastic system. The most famous and heroic fortress defense of pre-modern history. By establishing this moral or administrative benchmark, it continues to shape the structural and philosophical fabric of ancient Chinese statecraft.