The formation of the Janissaries has been dated to the reign of Murad I (r. 1362–1389), the third ruler of the Ottoman Empire. The Ottomans instituted a tax of one-fifth on all slaves taken in war, and it was from this pool of manpower that the sultans first constructed the Janissary corps as a personal army loyal only to the sultan.^[26]

From the 1380s to 1648, the Janissaries were gathered through the devşirme system, which was abolished in 1648.^[27] This was the taking (enslaving) of non-Muslim boys,^[28] notably Anatolian and Balkan Christians; Jews were never subject to devşirme, nor were children from Turkic families. There is however evidence that Jews tried to enroll into the system. Jews were not allowed in the janissary army, and so in suspected cases, the entire batch would be sent to the Imperial Arsenal as indentured laborers. Ottoman documents from the levy of the winter of 1603-1604 from Bosnia and Albania wrote to draw attention to some children as possibly being Jewish (şekine-i arz-ı yahudi). According to the Encyclopedia Britannica, "in early days, all Christians were enrolled indiscriminately. Later, those from what is now Albania, Bosnia, and Bulgaria were preferred."^[29]