Guerrilla warfare is basically 'Hit and Run' with a more sophisticated name. I'm not sure about why it was so successful in Vietnam, but I do know that Guerrilla warfare is very effective when executed properly, because there are very few casualties and a lot of damage is done to the enemy. It also works really well when the people using guerrilla warfare know the terrain well, because they would have an advantage over the enemy.
Hope this helps!
