Cavalry officer and legionary soldier, mid- 3 century CE. The foot soldier is drawn using equipment found in archaeological remains from the Siege of Dura Europos in Syria - 256 CE. (Romans vs. Sassanid Persians) Note that the longer spear was now used instead of the previously common pilum (javelin), the longer spatha (sword) replaced the famous gladius, suspended by a wider baldric sling.
Persian Sassanid (200AD to 600AD) in heavy armour, precursor of the European knights of the Middle Ages. All this heritage was swept away after the islamic conquest of Iran. The Sassanids were Zoroastrians like their predecessors' the Achaemenids and the Parthians, who ruled Iran from 500 BC to 600 AD.