Diocletian's Tetrarchy: Splitting the Empire

The instability that became the hallmark of the late Roman Republic rears its head again in the late days of the Empire. Today, we'll explore the following questions:

1. How did Rome's military manage to hold together the empire in the face of economic challenges?
2. What was happening in the Sassanian Empire at this time?
3. Why did Diocletian split the Roman Empire?