[ricree]

>The 3rd century is also when the Chinese Han Dynasty fell

And the Parthian empire, for that matter. At around the same time (the early 220s). An interesting timing for the three of them, although the worst of Rome's troubles didn't take place until decades later.

Not to mention how much the more aggressive Sassanid empire that followed the Parthians added pressure to the already troubled Roman state. Certainly, the Sassanid invasions played a very large part in Rome's own three way split from about 260-274.