re: #49 Kragar
Originally, Roman Legions were assembled in Rome, then dispatched to the provinces for garrison duties. Over time (decades), it was argued it was easier to man and recruit locals rather than spend the time and money it took to gather a legion in Rome and deploy it. This meant you ended up with a local military force comprised of Roman citizens, who began to wonder why they needed to actually listen to Rome when they were providing everything they needed for themselves.
I hold this to be a significant point in the collapse.
And why they should send tribute to Rome … .