the red horse that guo jing rode was no mystery to the song nation. this horse was discovered by a traveller during the han dynasty who wrote back and informed the emperor aboutt them as they had exceptional stamina and speed. the red blood sweat actually is caused by parasitic ticks on the horse that cause bleeding when the horses run and mixes with it's sweat. the emperor made a deal with the king of that land,Ferghana to supply him with breeding horses for his army and gave a princess as a bride in exchange. the princess wrote a peom about her sadness and homesickness, a famous line was "i drank wine,now i drink kuomiss" this incident was famous among the tang scholars peoms. however they could only supply about two thousand horses which wasn't enough, so the emperor invaded and conqured the Ferghana, who was backed by roman and german mercenaries. this incident later led to china's first contact with the west and the creation of the silk road. the red blood horse were included in china's defense against the xiongnu. this happened during the three kingdoms period.