Between 1200 and 1450, trade routes across Asia, the Indian Ocean and the Sahara carried more goods farther than ever. The Mongols linked much of Eurasia, merchants settled in foreign ports, and travelers wrote about what they saw. Along with silk, spices and gold came religions, technologies, crops and the plague.
Overland routes across Central Asia grew busier as commercial practices improved: caravanserai, credit, and money economies. Trade in luxury goods grew, trading cities such as Kashgar and Samarkand flourished, and Chinese, Persian and Indian producers made more textiles and porcelain for export.
The Mongols built the largest land empire in history, replacing collapsed states with khanates. By uniting much of Eurasia they made trade and travel safer and drew new peoples into trade networks, and they moved technologies and ideas between regions.
Knowledge of the monsoon winds plus the compass, astrolabe and larger ships expanded Indian Ocean trade, which built states such as the Swahili city-states, Gujarat and Malacca. Merchants formed diasporic communities that blended cultures, and Ming China's Zheng He sailed the ocean on huge voyages.
Camels, camel saddles and organized caravans made crossing the Sahara practical, expanding trade in gold, salt and enslaved people. The Mali Empire grew rich by controlling that trade, drawing West Africa into wider Afro-Eurasian networks.
Trade spread religions, literature, art, science and technology across Afro-Eurasia. Cities rose and fell with trade, productivity and disease. More travelers wrote about their journeys, and their accounts are sources you need to read with their point of view in mind.
Crops spread along trade routes and changed diets and farming, while pathogens traveled too. The bubonic plague spread along Eurasian trade routes in the 1340s and killed a huge share of the population in Asia, the Middle East and Europe.
The three networks share causes (better technology and commercial practices) and effects (rich trading cities, cultural and biological diffusion), but differ in geography, goods and the states they built. Strong comparisons name a category and support it with specific evidence.