How the world connected.

The Silk Roads ran ~4,000 miles from Han China to the Mediterranean. Goods: silk, porcelain, paper from China; horses from Central Asia; spices from India; gold and silver. Caravanserai inns hosted merchants and pack camels every 25 miles. Mongol Pax Mongolica (c. 1250–1350) made the routes safer than ever. Technologies traveled west: the magnetic compass, gunpowder, movable type, paper-making. Religions traveled too: Buddhism from India to China, then to Korea and Japan. The Black Death rode the same rails to Europe.

Genghis Khan (r. 1206–1227) unified the steppe tribes and conquered from China to Persia. By Kublai Khan’s reign (Yuan dynasty, 1271–1368), the Mongols had built the largest contiguous empire in history. Their rule was ethnically stratified but religiously tolerant, and they maintained the Silk Roads with brutal efficiency. The Mongol invasions destroyed cities (Baghdad, 1258) but also connected Eurasia: Marco Polo’s journey, William of Rubruck’s embassies, and the spread of gunpowder and paper to Europe all happened under Pax Mongolica.

The Indian Ocean was the world’s largest premodern trade network, driven by predictable monsoon winds. Arab dhows, Chinese junks, and Indian craft moved spices, cotton, gold, ivory, slaves, and horses. Major hubs: Mogadishu, Kilwa, Aden, Hormuz, Calicut, Malacca, Quanzhou. Diasporic merchant communities (Muslim, Jewish, Hindu) lived in foreign ports. Zheng He’s Ming “treasure fleet” voyages (1405–1433) reached East Africa with hundreds of ships—then China abandoned the project for political reasons, leaving the Indian Ocean to the Portuguese after 1498.

Berber-led camel caravans crossed the Sahara from the 8th century. Going south: salt, copper, textiles, manufactured goods. Going north: gold (West African Mali was one of the world’s richest sources), ivory, and enslaved people. The camel saddle was the critical technology that made bulk transport viable. Caravans concentrated in the Sahel cities (Timbuktu, Gao, Djenné), which became centers of Islamic learning. Mansa Musa’s 1324 hajj displayed Mali’s gold wealth so spectacularly that Cairo’s gold prices took a decade to recover.

Connectivity moved more than goods. Buddhism traveled from India to East Asia along the Silk Roads. Islam spread from Arabia to West Africa, India, and Southeast Asia along trade routes—often via Sufi mystics adapting to local cultures. Chinese inventions (gunpowder, paper, the compass) reached Europe by 1300. Hindu-Arabic numerals replaced Roman numerals in European mathematics. The Black Death (1347–1351) traveled the same network, killing ~75 million Eurasians. Connectivity has always come with biological cost.

Crops crossed networks: Champa rice spread from Vietnam to Song China, doubling agricultural output and enabling the population boom. Sugar cultivation moved from South Asia through Persian and Mediterranean Islam, setting up the Atlantic plantation system that came in Unit 4. Bananas moved from Southeast Asia to Africa. Citrus and cotton spread westward through Islamic agriculture. These weren’t neutral exchanges: domesticated crops reshaped land use, labor patterns, and demographic capacity.

Trade networks differ in technology, geography, and dominant carriers, but share the function of integrating distant economies. Compare: maritime networks (Indian Ocean) carried bulk goods cheaply; overland networks (Silk Roads, Trans-Saharan) carried high-value goods. State sponsorship varied: Mongol-protected vs. Berber-private vs. monsoon-coordinated. Diasporic merchant communities are common to all three. Use specific commodities and routes to ground the comparison.