In a game known as Rome Total War, the player may utilize cavalry for hammer and anvil attacks. When a player charges into an enemy battle-line from the rear, more often than not, the line holds strong, requiring the player to repeatedly cycle in and out, hitting them with numerous rear charges in order to cause the army to route.
How close to reality is this concept?
edit: To clarify, this is related to the second installment of the series: Rome Total War II.
edit2: Thank you everyone who contributed to answering this question! I feel I've gotten all the information I need. :)
It happened -sometimes- with elite units when the Cavalry retreated, took a break, and came back later. At Carrhae for instance the Parthian cataphracts charged the Roman legionnaires as they formed testudo to shield themselves against the Parthian horse archers, then retreated as they re-organized their lines to fight in melee combat. Then repeat this process as the horse archers fired on the Romans with arrows.
But in general this kind of tactic is pretty hard to pull off. The total war series is pretty inaccurate in terms of giving the player near perfect command and control over his/her troops. You have a perfect view of where all your troops are at any given moment, and you can instantly send orders which are instantly received and executed by your whichever units you issued them to and you can instantly observe whether those orders are working or not IN AN AGE WHICH WAS MILLENNIUMS BEFORE THE RADIO WAS INVENTED. This is something which may or may not be achieved even as of the 21st century on the battlefield.
In Ancient warfare, if you start to send orders you rapidly run into the problem of communication on a battlefield, your messenger might be killed, your troops might be too disorderly to carry them out, you also have no idea if your orders are actually carried out or not or even where they are sometime ( To give you some idea of this, even during the World Wars sometimes in the extreme chaos of combat division level headquarters have no idea where their units are.). Your troops might also not be trained/disciplined enough to disengage properly, let along reform themselves into battle order once they have done so.
So the act of ordering your troops to pull back from engaging in combat, reform them, and order them back into combat is a time-consuming process which requires supreme communication, discipline and training which most of the time are not available. Oftentimes commanders on ancient battlefield are restricted to deciding the placement of the troops, and where/when to send in your reserves.
This thread has a great discussion on the "pulse" model of fighting, in case you are interested: http://www.reddit.com/r/AskHistorians/comments/2c84kv/the_pulse_model_of_ancient_battles_what_are_the/