I believe the origins of its use are even later than Emperor Constantine. In fact, most early christians had no signs at all to show their christianity. It wasn't until the church really got going that symbols and relics started playing a part. Constantine pretty much started the idea of a symbol when he claimed the God appeared to him in a vision and told him to place a chi-rho sign on all the shield of his army and go forth and conquer. He obeyed and went on to destroy all of Maxentius army to a man, as the legend goes. The chi-rho sign is likely the predecessor to the cross being used. This happened in 312 CE. The Chi-Rho is a combination of first two letters of Christ in Greek, X and P. Early chi-rho signs essentially looked like a cross with a P on top. Thus a type of cross was made, and it morphed into the cross, then the cross with christ on it. After the reformation, the 'savior' was taken off the cross for two reasons.
1. To show that Jesus was not still on the cross
2. To show the world the difference between the protestants and the
catholic church.
Edited: konquererz on 3rd Apr, 2006 - 11:38am