Complex sentence: From gravestone inscriptions we know of the existence of "lanciarii" at least in one legion, "Legio II Parthica", which fought at Nisibis., which could skirmish forward and then withdraw to the safety of the heavier formations if necessary.
Split into simpler sentences: From gravestone inscriptions we know of the existence of "lanciarii" at least in one legion, "Legio II Parthica", which fought at Nisibis. They could skirmish forward and then withdraw to the safety of the heavier formations if necessary.