I've often seen a claim that with the Ottoman conquest of Constantinople, the Turks effectively "closed the silk road" to Europe, and that this was the impetus for Western European initiatives to find a western route to India and China.
Did the Ottomans actually shut down trade with Europe after they conquered Constantinople? I've read that trade embargoes were pretty rare in the Middle Ages, since many states relied on duties from trade as a major part of their revenue.
Was Ottoman policy a major break from normal Late Medieval-era Mediterranean trading policy? Or did they just charge unusually high taxes on trade with Europe? Or did they just levy fairly normal taxes, but Europeans were used to getting their spices through Genoese and Venetian merchants who had managed to extract extraordinary tax exemptions and privileges from the Byzantines and lost those privileges with the Ottoman conquest? Or is it just that the decline of the Mongol Empire lead to a proliferation of border-crossings throughout the silk road which made trade more difficult even though no particular individual power like the Ottomans was particularly anti-trade?
No, the Ottomans didn't block off trade. As it were, the volume of trade increased following the Ottoman conquests because they provided stability and consistent government to a previously fractured and warlike region. The voyages of discovery had more to do with Venice than with the Ottomans.
Venice struggled throughout the thirteenth, fourteenth, and fifteenth centuries to establish and maintain a trading monopoly in the Levant. Until the granting of capitulations to the French in the sixteenth century, anyone who wanted access to eastern goods had to go through the Venetian monopoly. By the end of the fifteenth century the Venetians' main competitor, Genoa, had largely been evicted from their eastern markets, and lost their previous Ottoman support.^1 What happened after 1453 was that the Venetian monopoly got stronger, which increased the desire of the Iberians to find a route to bypass it.
The one region the Ottomans did block off was the Black Sea, after 1475. Only Ottoman merchants were allowed access. They also embargoed Iran during the reign of Selim I (1512-20), but that postdates the discovery of the sea route to India.