Complex sentence: The backbone of "Spah" (middle-persian army) in the Sassanid era was their heavy armoured cavalry.These heavily armoured cavalry were noblemen which underwent extensive exercises in warfare and military manoeuvres through military training, gaining discipline and becoming truly elite soldiers.
Split into simpler sentences: The backbone of "Spah" (middle-Persian army) in the Sassanid era was their heavy armoured cavalry. This was formed by noblemen who underwent extensive exercises in warfare and military manoeuvres through military training, gaining discipline and becoming truly elite soldiers.