The most credible version of the history of Valentine's day can be traced back to third century Rome and the reign of Emperor Claudius the second. The emperor thrived on war, but his people eventually grew weary and refused to fight. Married men in particular did their best to stay out of the army. When the emperor decreed that there would be no more marriages, a young Roman Catholic priest named Valentine started performing secret marriages. Claudius called Valentine's marriages "acts of treason" and had the priest put to death.
Since then, Saint Valentine has been recognized as a martyr who sacrificed himself in the name of true love.