For 10 points, give this name shared by the son of Ardashir I as well as three Sassanid rulers, the first two of whom were known as "the Great".
Captives under one ruler of this name built the so-called Dam of Caesar in Shushtar. Another man of this name was declared emperor before his birth after his father died, and took Nisibis after winning the Battle of Singara. One ruler of this name defeated and killed Gordian III in a battle at Massice, which was renamed after him when Gordian's successor, Philip the Arabian, became his tributary. That ruler captured the emperor Valerian alive at Edessa and used his head as a footstool, while the second ruler of this name defeated Julian and Jovian after a protracted war against Constantius II, which included his capture of Armenia. For 10 points, give this name shared by the son of Ardashir I as well as three Sassanid rulers, the first two of whom were known as "the Great".
Captives under one ruler of this name built the so-called Dam of Caesar in Shushtar.
Shapur or Sabur or Sapor