In AD 260, the Roman emperor Valerian became the first — and only — Roman emperor to be captured alive by a foreign enemy after his defeat by the Persian king Shapur I at the Battle of Edessa.
Later Roman sources, especially the Christian writer Lactantius, claimed that Shapur humiliated Valerian by using him as a human footstool whenever he mounted his horse. These same accounts say Valerian died in captivity. Modern historians, however, caution that the "footstool" story may have been exaggerated or propaganda, as Persian evidence does not support those specific claims. What is certain is that Valerian was captured and never returned to Rome, making his fate one of the most humiliating episodes in Roman imperial history.
For a reputable overview, see the Encyclopaedia Iranica article on Shapur I:
Encyclopaedia Iranica – Shapur I
The account of the later Roman tradition about Valerian's humiliation, along with the modern scholarly caution about those stories, is well documented in historical sources.
https://www.iranicaonline.org/articles/shapur-i/https://ebrary.net/277528/history/capture_fate_valerian
