Though it was still powerful, by 1600 the Ottoman Empire had already entered a period of long-term and, eventually fatal, decline. The empire had reached the peak of its power during the reign of Suleiman "the Magnificent" from 1520-1566. However, the authority of the sultans was already being weakened by corruption and conspiracies at the court of Constantinople. The visirs (ministers) intrigued to obtain power at each other’s expense, and even the Janissaries (the elite regiments which formed the sultan's bodyguard) became less reliable. This meant that the beys (provincial governors) increasingly ignored Constantinople and ruled independently. By the late 18th century the Ottoman Empire became known as "the sick man of Europe".