Why can we say that 146 BCE was crucial in the formation of the Roman Empire, perhaps more than any other single year?

On Rome’s eastern borders was the Parthian (Persian) Empire. For a time Rome was able to take control of Iraq briefly but was unable to hold it for long. In Roman times Israel was called Judea.

But in the search for an answer, imagination can run wild. Suggestions have emerged in recent decades that attribute the rise and fall of ancient empires such as the Roman Empire to climate change and ...