The Silk Road Opens
When a Han emperor sent an envoy west to find allies against steppe raiders, the envoy returned with something more valuable: knowledge of a whole chain of civilizations to trade with. The route that opened — the Silk Road — carried Chinese silk to Rome and Roman glass to China, but far more importantly it carried religions, technologies, and eventually diseases across the whole of Eurasia. For the first time, a shock at one end of the world could ripple to the other — the first draft of a connected globe.
The path or medium of exchange moves, and a place or power rises or declines because it sits on or off the new route.