Complex sentence: Thus the Rhine was both significantly more accessible from Rome and better equipped to supply sizeable garrisons than the regions beyond, and there were also practical reasons to fall back from the limits of Augustus' expansionism in this region.
Split into simpler sentences: Thus the Rhine was both significantly more accessible from Rome and better suited to supply sizeable garrisons than the regions beyond. There were also practical reasons to fall back from the limits of Augustus' expansionism in this region.