"“Have you heard of the janissaries?”"

 The Janissaries were infantry units of the Ottoman Empire, which formed the household troops and bodyguards of the Sultan from the 14th century until 1826. The units were formed of children taken from non-Muslim households of conquered countries – chosen for their physical strength, they were taken at an early age so that they would forget their homes and grow up loyal to the Sultan. Intelligent children were chosen for the Enderun School, where they would be trained to become chemists, physicians or academics.

In speaking of the Janissaries, Bautista gives Changez something to identify with – in being ‘taken’ by Underwood Samson at an impressionable age, he feels he is being trained to be loyal to the American culture and so, ultimately, to betray his own.