Why was Valentine put in jail on Saint Valentine's Day?

Answer 1

Valentine was said to have continued to wed couples after Roman Emperor Claudius II Gothicus made it illegal, He needed to raise an army and could not draft married men. When he learned of Valentine's activities, he had him arrested, tortured and executed.

There is no doubt that at least one Saint Valentine existed, in fact, there are about 14 recognized by the Church. Confusion arises because two of these Valentines suffered martyrdom in Rome about the same time under Roman Emperor Claudius II Gothicus. One was a priest working in Rome and the second was Valentine the Bishop of Interamna, Terni, in Italy, who happened to be in Rome on Church business at the time. Their lives had become so intertwined and embellished by hagiographers over the years that it became impossible to separate them and the stories circulating. What was truth and what was legend? In 1969, due to this confusion, Saint Valentine was removed from the Calendar of Saints. His cult has not been suppressed so veneration is still allowed. However, any saint undergoing martyrdom for their faith is most worthy of veneration even if the whole story remains shrouded in mystery and legend.

Answer 2

The one fact that can be stated confidently is that we know nothing about the legendary Saint Valentine, not even whether he actually existed. Wikipedia says that it is uncertain whether St. Valentine is to be identified as one saint or the conflation of two saints of the same name, which if true would militate against any tradition that he was imprisoned or executed on a particular day. Nevertheless tradition says that he died on February 14, 273 on Via Flaminia in the north of Rome.

When, in 496, Pope Gelasius included Valentine among all those "... whose names are justly reverenced among men, but whose acts are known only to God," Gelasius implies that nothing was known to him about the life of Valentine. Subsequent tradition speaks of St. Valentine being arrested for secretly marrying young couples so that the husbands could avoid military service.