established libraries in their palaces, so that scholars might expand their knowledge and reap benefits from the work of their predecessors. The Fatimids were also known for their exquisite arts. Many traces of Fatimid architecture exist in Cairo today; the most defining examples include Al-Hakim Mosque and the Al-Azhar University. It was not until the 11th century that the Maghreb saw a large influx of ethnic Arabs. Starting with the 11th century, the Arab bedouin Banu Hilal tribes migrated to the West. Having been sent by the Fatimids to punish the Berber Zirids for abandoning Shias, they travelled westwards. The Banu Hilal quickly defeated the Zirids and deeply weakened the neighboring Hammadids. According to some modern historians. their influx was a major factor in the arabization of the Maghreb. Although Berbers ruled the region until the 16th century (under such powerful dynasties as the Almoravids, the Almohads, Hafsids, etc.), the arrival of these tribes eventually helped Arabize much of it ethnically, in addition to the linguistic and political impact on local non-Arabs. Ottoman Empire From 1517 to 1918, much of the Arab world was under the suzerainty of the Ottoman Empire. The Ottomans defeated the Mamluk Sultanate in Cairo, and ended the Abbasid Caliphate. Arabs did not feel the change of administration because the Ottomans modeled their rule after the previous Arab administration systems. In 1911, Arab intellectuals and politicians from throughout the Levant formed al-Fatat ("the Young Arab Society"), a small Arab nationalist club, in Paris. Its stated aim was "raising the level of the Arab nation to the level of modern nations." In the first few years of its existence, al-Fatat called for greater autonomy within a unified Ottoman state rather than Arab independence from the empire. Al-Fatat hosted the Arab Congress of 1913 in Paris, the purpose of which was to discuss desired reforms with other dissenting individuals from the Arab world. However, as the Ottoman authorities cracked down on the organization's activities and members, al-Fatat went underground and demanded the complete independence and unity of the Arab provinces. After World War I, when the Ottoman Empire was overthrown by the British Empire, former Ottoman colonies were divided up between the British and French as League of Nations mandates. Modern period Arabs in modern times live in the Arab world, which comprises 22 countries in Western Asia, North Africa, and parts of the Horn of Africa. They