The story dates back to the year 269, at that time Emperor Claudius II ruled the Roman Empire. The warring Roman army experienced an acute shortage of soldiers for military campaigns, and the commander was convinced that marriage was the main enemy of his military plans, because a married legionnaire thinks much less about the glory of the empire than about how to feed his family. And, in order to preserve the military spirit in his soldiers, the emperor issued a decree forbidding the legionnaires to marry.
But Valentine, as a priest, understood the injustice of the ban and continued to secretly marry his beloved.
From the ban of Claudius II, the soldiers did not become less in love. And to their happiness, there was a man who, not fearing the imperial wrath, began to secretly marry the legionnaires with their lovers. It was a priest named Valentine from a Roman city. Apparently, he was a real romantic, since his favorite pastimes were to reconcile those who quarreled, to help write love letters and, at the request of the legionnaires, on their behalf, give flowers to their beloved.
As soon as Claudius II found out about this, he decided to stop the "criminal activity" of the priest, and the priest was put in prison.
The tragedy of the situation was also in the fact that Valentine himself was in love with the jailer's daughter. While imprisoned, Valentine fell in love with the warden's blind daughter and healed her of her illness with his love. According to the legend, the jailer personally asked the priest to heal his daughter, and she fell in love with Valentine...
And, for beneficence and sinful love, he was sentenced to death, which took place on February 14.
The day before the execution, the priest wrote a farewell letter to the girl, where he spoke about his love, and signed it “Your Valentine”.
The letter was read after he was executed.
Subsequently, as a Christian martyr who suffered for his faith, Valentine was canonized by the Catholic Church.
And in 496, the Roman Pope Gelasius I declared February 14 to be Valentine's Day.

Since 1969, as a result of the reform of worship, Saint Valentine was removed from the liturgical calendar of the Catholic Church (along with other Roman saints, information about whose life is contradictory and unreliable). However, even before 1969, the church did not approve and did not support the traditions of celebrating this day.