One of those systems was devshirme--the practice of taking Christian children from their parents, converting them to Islam, and training them to become high-ranking government officials or members of the Janissary, the most elite soldiers in the empire. Soldiers of the Janissary were expected to adhere to a rigid set of rules for personal conduct. They were not allowed to marry, and had little contact with those outside their own units. The Janissary were fiercely loyal to one another, a quality that made them excellent soldiers but one that also made them feared and resented by the local population. Some members of the Janissary became very wealthy and powerful. All became the most feared and respected soldiers in Europe, as two centuries of continual conquest and expansion made the Ottoman army the greatest of its time.