The most famous example is probably Philippides in the Battle of Marathon.  Humans can run longer distances than horses, and is a [key hunting tactic][1] employed by hunter and gatherer societies when they are chasing four-legged prey.  Knowing this, we have the reason why Philippides was sent on foot instead of on a horse.


  [1]: https://en.wikipedia.org/wiki/Persistence_hunting#Human_persistence_hunting