The Spanish Conquest laid the ground for 300 years of colonial rule which made Spain the richest country in Europe and divided Mexico with a class system that still affects today's society. After the conquest, Mexico became the world's largest producer of silver which fueled Europe's trade with Asia. Meanwhile, conquistadors and friars spread out along so called "royal roads" which linked with the desert frontiers of the north, attempting convert Apache and Comanche tribes who would battle Spaniards, Mexicans and Americans for centuries.