Complex sentence: The main impression that historians once retained from the "Historia" focused on Gregory's anecdotes about violence; until recently, historians tended to conclude that Merovingian Gaul was a chaotic, brutal mess.
Split into simpler sentences: The main impression that historians once retained from the "Historia" focused on the violent anecdotes that Gregory relates. Until recently, historians have tended to conclude that Merovingian Gaul was a chaotic, brutal mess.