Short answer: The Silk Road traveled northwest rather than southwest mainly because the northwest route offered fewer insurmountable barriers and better relay points for long-distance caravan trade, especially through Central Asia, compared to the more formidable mountain ranges and plateaus to the southwest. Context and key factors

• Geographical barriers: The southwestern route would have to cross the Himalayas and Tibetan Plateau, which posed extreme elevations, harsh weather, and challenging passes for caravans and pack animals. In contrast, the northwest path through Central Asia offered more navigable passes and large oasis towns along established caravan routes.

• Availability of nodes and infrastructure: The Silk Road developed vast networks of oasis towns, caravanserais, and markets in Central Asia and the Ferghana Valley, which made long-distance trade along the northwest corridor more practical and safer for merchants. These hubs facilitated rest, trade, and protection.

• Political and security landscape: Periodic state and tribal polities along the northern and central routes provided governance, protection, and taxation of caravans, which helped sustain long-distance traffic. The southwestern routes faced different geopolitical dynamics and expansion barriers that could disrupt continuous passage.

• Maritime and overland complementarities: While sea routes later expanded trade networks, the overland northwest corridor aligned with early Chinese exports (notably silk) heading west, leveraging established Silk Road nodes before the rise of sea lanes.

Notes for further reading

• The Silk Road was not a single thread but a network with multiple routes, including northern and southwestern segments, with shifting prominence over centuries depending on political stability, climate, and demand.

• Various scholarly discussions highlight that northern routes through Central Asia often served as the primary arterial pathways for long-distance overland trade, with desert and mountain barriers shaping the choices merchants made.

If you’d like, I can pull more detailed, source-backed explanations for specific segments of the route (e.g., Chang’an to Dunhuang, or the Kokand- Gaziantep axis) or compare the northwest and southwest routes across different historical periods.