Emperor Constantine the Great: Pagan, Christian, or First Pope?

This is a reply to the claim of some Protestant fundamentalists that the Roman Emperor Constantine the Great or Constantine I (born c. 280 - died 337 A.D.) remained a pagan, was never a Christian, and was the first Pope. Here is a typical false history believed by fundamentalists. The following was posted on the Catholic Answers boards:

When Christians were on the verge of growing, Satan's forces started to move. Persecutions, under Satan's command, hit the early believers in Christ. But instead of destroying them, they grew in numbers. The Force was ruling over Rome, using the Pagan Roman Caesars to slaughter the followers of Christ. The time was getting close for Satan then to give the world his own version of the 'Christian' church. And paganism was about to get a new face. When the Emperor of Rome died, two men claimed the throne: Constantine, and the other Roman General named Maxentius.

In 312 AD, Constantine's army faced his enemy, Maxentius, who stood between him and the Roman Empire. It was during this battle when he 'apparently' saw a sign of the cross in the heavens saying, 'In this sign Conquer.' Having backed up by 'The Force,' he won the battle