Supernatural Tactics of the Mongols
The Mongols even resorted to supernatural means to assure their success. They asked Tenggri, or Heaven, for his favor on the battlefield, in the same way that Muslim and Christian armies appealed to their god. But the Mongols also employed other supernatural tactics, of which the most important was weather magic, conducted by a shaman known as the jadaci.
Several accounts mention the use of weather magic. The jadaci used special rocks known as rain stones, thought to be imbued with the power to control weather, in order to summon rainstorms, or even snowstorms in the summer, which caught the enemy ill-prepared. The Mongols, who had lured their opponents away from their base, took shelter during the storm and then attacked while their foes were disoriented. A prime example of this tactic was recorded during the war against the Jin after Chinggis Khan’s death. Bar Hebraeus relates that Ögödei resorted to using rain stones after he saw the size of a Jin field army. After he had lured the Jin away from any support, he called upon his jadaci to summon a storm. The ensuing downpour, in the normally dry month of July, lasted for three day and three nights. The Jin army was caught in the open and drenched while the Mongols donned rain gear and waited the storm out. They then turned around and ambushed the Jin army, annihilating it.
Other sources indicate that Tolui, rather than Ögödei, was the general involved in this episode. Tolui had retreated after encountering a much larger Jin force, and after the Jin had attacked his rearguard he summoned a Turkic rainmaker to perform his magic. Rashid al-Din recorded that ‘this is a kind of sorcery carried out with various stones, the property of which is that when they are taken out, placed in water, and washed, cold, snow, rain and blizzards at once appear even though it’s the middle of summer.’ The rain continued for three days, changing on the final day to snow accompanied by an icy wind. The Jin troops were exposed to this severe weather while the Mongols found shelter. After four days of snow, the Mongols attacked and destroyed the bewildered and weakened Jin troops.
This is the first explicit reference I have found of the use of magic in warfare.