Historical legend dictates that Napoleon's horse was called Marengo, and he rode the horse in all his battles including Waterloo. Historical fact suggests that this is untrue, in fact none of the 80 horses registered at Napoleon's stables was listed under that name. Since Napoleon had more than a dozen horses killed under him in various battles, the chances of one horse surviving his entire military career are remote.
Napoleon was a poor horseman, having learned to ride on the lowly stock of his native Corsica. His posture was acknowledged as dreadful, given his status, and all his horses had to receive extensive schooling to ensure they remained calm in the heat and noise of battle, thus saving the Emperor's dignity, and possibly his life.
The legend of Marengo is possibly a result of French historians' wilingness to increase the stature of their national hero with the attractive notion of a faithful steed present at all his triumphs. The reality is that Napoleon was indifferent to which of his horses transported him into battle, each indistinguishable from its stable-mates - all the small Arab stallions he favoured.
Marengo is the horse of legend, and it seems that is exactly what he was - a myth with little basis in fact.