Nevertheless, the change of dynamics in the European states system with the end of Dark Ages after the 15th century with Renaissance and Reformation movements, on the one hand, and geographical discoveries, on the other, the Ottoman Empire faced new challenges and started to decline. However, the decadence of the Ottoman power cannot be explained only by external factors. In other words, after the 16th century, the empire was not ruled by strong and competent rulers as Mehmed II, Selim I and Suleyman I. The administrative system and the palace were full of problems. In addition, especially after mid-1600s, the Ottoman economy started to weaken with the end of territorial expansions, discovery of new routes and defeats in wars with stronger European states as a result of the formation of modern states and armies. Lastly, but more importantly, the Ottoman military system which was the major source of Ottoman power began to decline after the 16th century. Janissaries as the crux of the Ottoman military power lost their discipline and prestige as well as their adaptation to modern war techniques and tactics.