King Clovis the 1st became king of a small region of what is now France in 481 when his father died. He was only 15 years old. Using a powerful army and creative tactics he quickly consolidated his power to include most of what is now France. After a very successful battle he converted to Catholic Christianity.
His conversion began the process of making Catholicism the dominant religion in France for the next 1500 years.
In many ways he was the right man at the right time. Rome had ruled most of France for many centuries and with their decline it was easier for a man like Clovis to gain power.