Who is considered a hero is a delicate matter. To be precise, it's a very subjective thing. For example, for a group of people, local or national hero can be a symbol of independence or resistance against the occupants (e.g. Vercingetorix, Boudicca), even if the hero him/herself wasn't really successful in the uprising. Some outlaws are also considered heroes, e.g. Robin Hood or Janosik, and it's difficult to say if their actions were really that great or not cowardous ("Ha, they were running away from the government - COWARDS!!"), while some influential people in the history are viewed as "badguys" because of a single book or movie (e.g. Cardinal-Duc de Richelieu and the book "The Three Musketeers").

It's not really that different in case of ambushes, horse archers and guerilla warfare. Some will call it the "cowardice", while the others will call it the "tactics". As I said in my previous post, personally I consider this tactics. I think that it doesn't matter what path to victory will someone choose, it's the effect that is important. Tortures, assassinations, exterminations, slavery, ambushes or open field battles - who cares, when you achieve your goal? I mean, all that heroic stuff is good to glorify in tales and legends, but the reality is - all is fair in war (and love...). Or even better - even if something is not "fair" or moral, you can't decline the possibility that your enemy will use it against you.