May God be with you.

Paul was a Jewish Talmudic student. He was a Pharisee, a Tent-maker by trade. Saul the Jew hated and persecuted Christians as heretical, even assisting at the stoning of Saint Stephen the Martyr. On his way to Damascus to arrest another group of them, he was knocked to the ground, struck blind by a heavenly light, and given the message that in persecuting Christians, he was persecuting Christ. The experience had a profound spiritual effect on him, causing his conversion to Christianity. He was baptized, changed his name to Paul to reflect his new persona, and began traveling and preaching.

(source - Patron Saints Index)

God bless you!
this explains why there was 12 again.a new apostle chosen by jesus ,he reformed the worst sinner to show us everyone can be saved.
Paul was indeed a man driven by His love for Jesus for once He beheld His glory He was to spend the rest of His life trying to put it into words and share it with others. Roughly 60 times he used the phrase " in Christ" for that is were he spent his life seeking to dwell so he was indeed a soldier for Christ but no gladiator:D