A horse named Smokey was the star of performances requiring dragging someone from the stirrup. Smokey got the Craven award in 1966 for all the tricks. Each horse had to be taught individually then in pairs then three till all four horses to pull the chariot. There were 9 chariot teams. 72 horses were trained only 36 where in the film.
Horses have understudies just as people.
The Lippizan team who leaped the chariot over several crashed vehicles were trained weeks ahead and practiced as dancers do - leaping higher than required for the scene. Sorry to say Glenn Randall Sr . has passed away in 1993. Glen Randall Jr. also continues to train the horses for your movie favorites. Universal Studios Wild Wild West Show stunt horses were trained by the Randall family. The horse saved the pony from being stolen by opening the horse trailer door as it was moving down the road.