Excerpts from Books and Wikipedia
Rome was falling after invasions by barbarians, runaway inflation, and civil war. Further damage was done as Emperor Valerian was captured by the Sassanian Persians at Odessa. Persia was ruled by other kingdoms until 224 when the Sassanian dynasty came to power. The Sassanians sought to attain world power equal to the Persian Achaemenid dynasty of 559-330 BC. Following the Battle of Edessa, Britain and Gaul declared independence, and the "Thirty Tyrants" fought for the throne in the east empire. [Furtado: 1001 Days]