Egypt, officially the Arab Republic of Egypt, lies in northeastern Africa with the Sinai Peninsula, the easternmost portion of the country, forming the only land bridge between Africa and Asia. Egypt’s strong identity extends back to the 4th millennium BC when ancient Egyptian civilization developed along the Nile River. A unified kingdom with a recorded history since about 3200 BC, Egypt was ruled by a series of dynasties for three millennia. Arab rule in the 7th century introduced Islam and the Arabic language. Egypt gained partial independence from British rule in 1922 and full sovereignty after WWII. The Arab League was founded in Cairo, where it remains headquartered, and President Gamal Abdel Nasser emphasized the ideas of Arab unity and socialism. Present-day Egypt remains one of the most important centers of Arab culture in the Islamic world. It also retains important aspects of its past Christian, Greco-Roman, and ancient indigenous heritage. In 1979, President Anwar Sadat negotiated an historic peace treaty with Israel, dramatically changing the politics of the region. The most populous Arab country, Egypt has great economic potential yet faces social, political and economic obstacles.