Complex sentence: Shapur II reformed the army by adopting heavier and more effective cavalry, being clad in iron and bodies were covered with thick plates, some being armed with pike and some with sword and mace they were looking like moving statues.
Split into simpler sentences: Shapur II reformed the army by adopting heavier and more effective cavalry. These mounted units were clad in iron with bodies covered with thick plates, some being armed with pike and some with sword and mace they were looking like moving statues.