The Janissaries by Godfrey Goodwin
From the fifteenth to the sixteenth century, the janissaries were the scourge of Europe. Their ferocious spirit allowed their masters to extend their conquests from the Danube to the Euphrates. Their power was such that even sultans trembled.
But by the end of the eighteenth century, they were more interested in trade than war. Ill-disciplined and arrogant, both rulers and ruled turned against them. Yet their political power was so extensive it took years before they could be suppressed.