According to www.dictionary.com
jan·is·sar·y Pronunciation Key (jn-sr) also jan·i·zar·y (-zr)
n. pl. jan·is·sar·ies
1. A member of a group of elite, highly loyal supporters.
2. A soldier in an elite Turkish guard organized in the 14th century and abolished in 1826.
Sometimes spelt Janizary. The Janissaries were Turkish elite corps in the standing army of the Ottoman Empire during the late 14th century. They were first called Yeniceri, new soldier or troop in Turkish. It was Sultan Murad I who created the group, capturing Christian youths from the Balkans, and forcing them into the Muslim belief at gunpoint. These Christian converts were regarded as cannon fodder, and so they were trained to fight on the front lines of Turkish armies, to perhaps preserve the more important Muslims.
This group of cannon fodder, however, became the most feared and respected military force in the Middle East. After years of serving on the front lines, the Jannisaries emerged as elite forces and incredibly pious Muslims. At this stage they were organised into three divisions, the Cemaat, Bölükhalki and Segban. The Janissaries were subject to strict religious doctrine, such as celibacy, however this doctrine was abandoned in the late 16th century. The Janissaries ceased to recruit and began to become their own force, no longer controlled by the government. They began leading many Jihads to reclaim territory deemed as Holy Lands, and lead political coups to overthrow any Sultan giving them grief.
The Janissaries were tolerated until the early 19th century when the Ottoman Empire began introducing European reforms into its army. The Janissaries were highly fanatic, and incredibly religious, believing that Europeans were anti-Allah and their ways were not to be tolerated. They led a Jihad in open rebellion againsy Sultan Mahmud II, ruling at this time. Mahmud II reacted quickly, declaring war on the Rebels and stormed the Janissaries' headquarters in June 1826, surrounding the place and bombarding it with cannon fire. Most of the Janissaries were killed in the siege, however some escaped and were captured, later executed by the Sultan's forces.