The Mongols Hated Sieges

Because they are much harder than battles

Here is a tale of technological globalization. The Crusades spurred a regional arms race in siege weapons. Arabs illustrated and improved on the engines that crusaders brought against them from Byzantine lands. Selling their services to the Mongols, Arab engineers then participated in the vast campaigns of the Golden Horde throughout Jin China, Russia, Hungary, and Persia.

The last case is especially notorious: Khwarazmshah brought the Golden Horde down on his own head by killing ambassadors of the Mongol court. Tolui, a son of Genghis Khan, subjected Khorasan to utter brutality, destroying every city and population which did not submit.

A 14th Century manuscript of Rashid-al-Din Hamadani’s Jami’ al-Tawarikh (Compendium of Chronicles) held at the University of Edinburg Library includes an illustration of a counterweight trebuchet in action during one of these sieges (see above). It is a very-evolved sling. Note the turbaned Arab specialist handling the ammunition; some troops engage in an archery duel with the defenders, while others walk on the treadmill mechanism that cocks the trebuchet in place.

Moreover, the wall is brick, which turns out to be a very resistant material even against gunpowder cannons. Nevertheless, the Yuanshi (History of Yuan) records that a Muslim trebuchet struck a gate tower of Xiangyang in 1272, “making a sound like a clap of thunder and shaking the inside of the city.” The Song general, we are told, capitulated after the engine opened a breach. One wonders just how big the breach really had to be: traditionally, the opening of a breach is the last opportunity for a garrison to surrender on any terms at all.

Virtually undefeated on the battlefield, Mongols had a mixed poliorcetic record, finding progress most difficult wherever stone fortifications were most complete: northern China, Korea, Krakow. A growing preponderance of advanced fortifications the further they advanced west appears to have been a factor in the Mongols’ decision to discontinue the invasion of Europe in 1242 after the death of Ögedei Khan.

Indeed, the only Khan ever killed in combat was likely felled by an artillery projectile during the siege of Diaoyu Fortress in China. It may have been a large crossbow bolt or a stone; primary sources are understandably unclear, since such a death would be distasteful to Mongols.

It proved to be a history-making bullseye, however. Upon hearing of the death of Möngke, son of Tolui, Hulagu Khan withdrew from Palestine and the ashes of Baghdad to carve out a private dominion in Persia. Kublai Khan would finish off China after a civil war with his younger brother, but the unity of the Golden Horde had been smashed forever, lucky for Europe.

Nor was Kublai Khan eager to repeat the success at Xiangyang over and over again. Adopting a new strategy that required a navy, the campaign which eventually succeeded in subjecting China went around the fortified line of cities into more open country by way of the river systems.

Put simply, Mongols hated sieges. Sitting in one place for very long was contrary to the spirit of a martial culture that valued open space and maneuver, to be sure, but the conditions of a Mongol camp were a more serious consideration. As long as the horde kept moving, sanitation was no great issue. Once they stopped to invest a city, however, disease and dehydration took a greater toll on them than battles.

Worse, even a large breach in any wall required the Mongols to dismount in order to exploit it. Riding on their ponies, Mongols were supreme; on foot, man to man, stumbling over rubble and splashing through mud, they were no more fearsome than any other kind of warriors. Mongols required their subjected populations to provide levies, and a primary use of these unwilling troops was ‘cannon fodder’ for storming breaches.

Then there was the digging. Mongols did not enjoy digging. It was menial, and moreover the work of farmers, which they held as the lowest occupation. Sappers, engineers, and storming duties were therefore left to others, and the Mongols never developed any of these siege-related specializations in their own society. Crossbows were yet another siege technology they never took home.

Historians argue whether, or to what extent, a Pax Mongolica allowed the transfer of goods and technologies along the Silk Road, spurring the European Renaissance and globalization. Perhaps the more instructive analysis is that the Mongols faded from history because they did not transfer these technologies to themselves. Siege was not the kind of war they enjoyed, or were good at, and so they chose not to learn how to win at it.