Jin soldiers defended the city with fire lances and bombs of gunpowder, killing many Mongols and severely injuring others.

The Jin dynasty tried to arrange a peace treaty, but the assassination of a Mongol diplomat foiled their efforts.

The city was placed under the command of General Cui Li, who executed the emperor's loyalists and promptly surrendered to the Mongols.

The Mongol strategy was based on capturing small settlements and ignoring the fortifications of major cities.

The Mongols were not able to penetrate the walls of the city in the Battle of Zhongdu, but intimidated the Jin emperor into paying tribute.

[11] In Manchuria, the Khitans, under the leadership of Yelü Liuge, declared their independence from the Jin and allied with the Mongols.

Yelü was enthroned a puppet ruler subordinate to the Mongols in 1213, and given the title emperor of the Liao dynasty.

Wannu, realizing the Jin dynasty was on the verge of collapse, rebelled and declared himself king of Eastern Xia in 1215.

[14] After the fall of Zhongdu in 1215, the Mongols downsized their war effort against the Jin, and shifted their resources in preparation for the invasion of Central Asia.

There was some progress towards an agreement in the summer of 1232, but the assassination of the Mongol diplomat Tang Qing and his entourage by the Jurchens made further talks impossible.

The Jurchen emperor was afforded the opportunity to escape in late 1232, and departed with a retinue of court officials.

[25] The Mongols looted the city when it fell, but atypical to most sieges in the time period, they permitted trade.

The richest residents of the city sold their luxury belongings to Mongol soldiers for critically needed food supplies.

[21] Many of the details of the siege are known to historians, based on a comprehensive account of the battle compiled by a Jin official living in the besieged city.

The bomb produced a large explosion the moment it landed, inflicting damage that could penetrate armor.

The explosion sometimes sparked a fire on the grass of the battlefield, which could burn a soldier to death, even if he survived the initial blast.

[27] Mongol soldiers counteracted the bombs by digging trenches leading up to the city, which they covered with shielding made of cowhide, to protect from the explosives fired overhead.

[24] The Jurchen official reports, in a translation provided by historian Stephen Turnbull: Therefore the Mongol soldiers made cowhide shields to cover their approach trenches and men beneath the walls, and dug as it were niches, each large enough to contain a man, hoping that in this way the troops above would not be able to do anything about it.

When these reached the trenches where the Mongols were making their dugouts, the bombs were set off, with the result that the cowhide and the attacking soldiers were all blown to bits, and not even a trace being left behind.

[28][29] The mixture contained, besides the gunpowder ingredients of sulfur, charcoal, and saltpeter, ground porcelain and iron filings.

[28] The heated tinder that ignited the weapon was stored in a small iron box toted by the Jurchen soldiers in battle.

Herbert Franke maintains that gunpowder was in the arsenal of both combatants,[21] but Turnbull believes that only the Jurchens made use of it.

[24] The Mongols loaded their catapults with large stones or bombs of gunpowder, which were fired at the Jin fortifications.

The Song, who had fought multiple wars against the Jin, resented the Jurchens for their conquest of northern China decades earlier.

Historian Patricia Buckley Ebrey noted that the Mongol Yuan dynasty treated the Jurchen Wanyan royal family harshly, butchering them by the hundreds as well as the Tangut emperor of Western Xia when they defeated him earlier.