Excerpts from Books and Wikipedia
"He was taken captive by the Persian Emperor, Shapur I, after the Battle of Edessa, becoming the first Roman emperor to be captured as a prisoner of war, causing shock and instability throughout the empire. . . . While fighting the Persians, Valerian sent two letters to the Senate ordering that firm steps be taken against Christians. The first, sent in 257, commanded Christian clergy to perform sacrifices to the Roman gods or face banishment. The second, the following year, ordered the execution of Christian leaders. . . . It also decreed that Roman matrons who would not apostatize should lose their property and be banished, and that civil servants and members of the Imperial household who would not worship the Roman gods should be reduced to slavery and sent to work on the Imperial estates. This indicates that Christians were well-established at that time, some in very high positions." [Wikipedia]