After the capture of Constantinople, the Ottoman Empire changed the name to Istanbul and began to expand rapidly thereafter. The Ottomans had originally used an army that had two separate forces, one was a light cavalry and the other volunteer infantry. Throughout the Ottomans expansion, they rapidly improved their military strength through the use slave troops known as Janissaries. The Ottomans bordering neighbor was the Safavid Empire. The Safavid Empire under the rule of Shah Ismail tried to control the masses with political propaganda, which used various stories of their choosing to explain the events that unfolded however they desired. The Ottomans converted many Christians to Islamic religion, whereas, the Safavids often chose to follow