The correct answer is the fall of the Mongols and the fall of the Byzantine empire which led to a decrease in trade.
Under the leadership of Mehmet II, in 1453, the Ottomans captured the capital of the Byzantine Empire, Constantinople.
The three great civilizations of Rome, Han(China), and Gupta(India) collapsed due to invasions by armies from central Asia. Rome was invaded by Germanic troops, considerably affecting trade. Christianity, Buddhism, Hinduism, and Islam extended to various regions. This new time saw the birth of monotheism and a new form of civilization. From China, new civilization spread to Korea and to Japan. Byzantine civilization expanded north to was later known as Russia.
