A controversial institution typical of the Ottoman system was the devshirme (translated: collection). Introduced by Sultan Murad I (r. 1362-1389), it involved "taking" children of Christian origin and family from their homelands—primarily from the Balkans, largely conquered by the Ottomans during the 14th century—and sending them to the Sultan's court. Upon arrival at court, many of them would convert to Islam, undergo circumcision, and be trained to become palace officials. It was not uncommon for the Grand Vizier—or other prominent members of the Ottoman hierarchy—to have been recruited through this practice. A prime example is Sokollu Mehmed Pasha, who hailed from a family belonging to the lesser Serbian-Bosnian Orthodox nobility and became Grand Vizier during the reigns of Suleiman I (r. 1520-1566) and Selim II (r. 1566-1574). In general, one objective of this institution was to create a new class of servants entirely loyal to the Sultan, as Marc David Baer rightly points out in his summary of the Ottoman Empire. In addition to administrative-political officials, many of these children were trained as soldiers, forming the feared Janissary corps, whose name in Ottoman Turkish means "new army" (Yeniçeri). Another clear objective of the devshirme was the absorption and integration of enemy elites in conquered territories; however, it was very common for conscripts to remember their place of origin well. Sokollu himself used imperial resources— to which he had full access as Grand Vizier—to build a bridge over the Drina River, an essential infrastructure for his homeland. A very fitting and now indispensable source is "Memoirs of a Janissary". It is the autobiography of a certain Konstantin, a Serbian child who was "collected" through the devshirme and included in the Janissary corps, participating in the siege of Constantinople in 1453.