They still thought of the Sassanids to be no different than the Parthians, however, the Sassanids were much different in terms of aggressiveness and nationalistic zeal and the Romans would soon realize this. The Romans sent a delegation to ask for Persian withdrawal, noting the past defeats of the Parthians by the Romans as a warning. Ardashir rejected and in 231 Rome mobilized for war under Severus Alexander, drawing troops from Egypt to the Black sea to form three massive armies.