Aliens and UFOs in history

On October 26 the year 312 of our era, the Roman Emperor Constantine I was kneeling facing the sun, adorable, when there was a strange phenomenon. Coming of astro king, the emperor was right to see some dark radiation diagonally to draw a bright and powerful cross on the sky.

In his mind resonated then a name-and-Christos, then the same supernatural voice told him:
"With this sign, triumph." Constantine did not think twice. Still perplexed by this mirage or dream, ordered his men replacing the imperial eagle that appeared in the aegis of its troops and banners by the symbol of Christ.

It was the dawn of October 27 troops were awaiting the arrival of Constantine in the gorge at the foot of the bridge Milvaiano, the numerous enemy ranks who were under the command of Marcus Aurelius Maxentius.

The battle was fierce but Constantine won. Is it due to the victory announced by the strange luminous phenomenon? Or simply superstition served as a positive impetus to the Roman troops suggestions? In either case, Constantine managed to defeat Maxentius and enter victorious in Rome.

Probably nothing would be like today if that "vision" had not occurred. Christianity, surely, would have been prosecuted and punished for Rome and the foundation of our Western civilization had not developed as they have done.
Do UFOs could alter the development of history? The occasion previously reported is not the only one we know.