For centuries the Arabian Peninsula was inhabited by loosely connected tribes. The tribes were polytheistic, but they placed special emphasis on a supreme god named Allah. Muhammad, who grew up in Makkah, believed that he received revelations from god. Out of these revelations came the Quran, the holy book of Islam. Islam is a monotheistic religion with an ethical code based in part on the Five Pillars of Islam. Muhammad started preaching and forming the first communities of Muslims. He and his followers were persecuted in Makkah and moved north to Madinah. There Muhammad became both a religious and a political leader. After eight years in Madinah, he led a military force that easily conquered Makkah.