Complex sentence: Before the battle, Shapur I had penetrated several times deeply into Roman area, and conquered and pluendered Antiochia in Syria in during 253 or 256, in order to halt and retaliate, Emperor Valerian gathered a huge army and marched eastward to the Sassanid borders.
Split into simpler sentences: Before the battle, Shapur I had penetrated several times deeply into Roman area, and conquered and pluendered Antiochia in Syria in 253 or 256. In order to halt and retaliate, Emperor Valerian gathered a huge army and marched eastward to the Sassanid borders.