Why does the bishop slap your face when confirmed?

It represents a slap more than a touch, I for got my confirmation but I think the "Slap" is to signify that you have become a soldier of christ.
Since the reform of the Rite of Confirmation in 1971, this is no longer done. In the older rite, the bishop would strike each candidate on the cheek, symbolizing that the Christian is now a soldier for Christ and must endure suffering and the persecution that comes from conflict with the world. This was supposed to be done gently, although I'm sure there are many parents and grandparents among us who may recall a rather robust reminder by the bishop of the trials of the Catholic life!