Sipahi were two types of Ottoman cavalry corps, including the fief-holding provincial timarli sipahi, which constituted most of the army, and the regular kapikulu sipahi, palace troops. Other types of cavalry which were not regarded sipahi were the irregular akıncı (“raiders”). The sipahi formed their own distinctive social classes, and were notably in rivalry with the Janissaries, the elite corps of the Sultan.
The term refers to all freeborn Ottoman Turkish mounted troops other than akıncı and tribal horsemen in the Ottoman army. The word was used almost synonymously with cavalry. The sipahis formed two distinct types of cavalry: feudal-like, provincial timarlı sipahi (timariots) which consisted most of the Ottoman army, and salaried, regular kapıkulu sipahi (sipahi of the Porte), which constituted the cavalry part of the Ottoman household troops.
The provincial governors, or beys, were rotated every few years, preventing land inheritance. The provinces, or sanjaks, were not all equal since Anatolia and the Balkans were mostly ruled by Turks, while other areas of the empire were more flexible, adhering, somewhat, to local traditions.
The entwinement of land, military, politics, economics and religion was a way of life. The timar system, where the sultan owned all land but individual plots of land, came with residential rights. The Ottoman people had rights to the land but the sipahi, a unique kind of military aristocracy and cavalry portion of the military, also lived on the land with the farmers (90% of the population) and collected tax revenues, usually in-kind, to subsidize the costs of training and equipping the small army, dedicated to serving the sultan. The sipahi did not inherit anything, preventing power centres from growing and threatening the supreme power structure. The locals on the timar used the land and all it produced