At the following map you can see the Islamic World at around 1500 C.E. All the empires that you see colored on the map were Islamic empires. Moreover the Muslims were controlling the Straits of Malacca, which connect the Indian Ocean to the South China Sea. Even today the Chinese and the Americans are confronting each other at the Malacca Straits and the South China Sea, because China claims the whole of South China Sea, and the Americans do not accept that.
You can see how much pressure there was on Western Europeans i.e. the Portuguese, the Spanish, the French, the English and the Dutch. All of them had to buy from the Muslims the exotic goods of Asia i.e. silk, spice, porcelain etc. The Muslims would not allow them to exploit the trade routes for themselves, and they had to buy these goods from the ports of the East Mediterranean Sea, which were all controlled by the Muslims. This is the time before the English industrial revolution, which transformed Western Europe the factory of the whole world. At this point in time the European economy is still an agricultural economy, and the Western Europeans have to pay high prices to the Muslims the get hold of the exotic goods of Asia.
The Western Europeans turn to the Atlantic, and the Portuguese discover a route to India around Africa (Vasco Da Gama 1497), and the Spaniards, in their effort to find a route to Asia that would bypass the Islamic World, they discover America (Columbus 1492).
For the Western Europeans trade shifts from the Mediterranean Sea to the Atlantic Ocean, and power in Europe starts shifting from Venice, and the other Italian city states, to the European countries of the Atlantic. Venice, and the other city states of Italy were controlling the spice trade in the Mediterranean, and they were carrying the goods of Asia to Europe, from Alexandria (Egypt), Constantinople (today’s Istanbul), and Beirut (today’s Lebanon).
The Western Europeans will start fighting each other for influence in the New World (America), and for the new trade routes to the New World and to Asia. The Spanish found a very convenient way to get hold of the goods of Asia. They conquered Mexico and Peru in America, where they discovered mountains of silver and gold. They also conquered the Philippines, and they were sending their silver from Acapulco (Mexico) to Manila (Philippines), and in exchange they would get goods from China and Asia. The term Manila Galleons refers to the large commercial ships of Spain, that were carrying silver from Mexico to Philippines, and oriental goods from Philippines to Mexico. This Spanish business was taking place for the period 1565-1815.
When the Spaniards conquered Mexico and Peru, they defeated the Aztecs and the Incas. Both were very tough guys, who were hated by the other local populations who were oppressed by them. The Spaniards, who were by far outnumbered by the Incas and the Aztecs, allied with their enemies and defeated them.