Sudan ( or ; , ), officially the Republic of the Sudan (), is a country in Northeast Africa. It is bordered with the Central African Republic to the southwest, Chad to the west, Egypt to the north, Eritrea to the northeast, Ethiopia to the southeast, Libya to the northwest, South Sudan to the south and the Red Sea. It has a population of 45.70 million people as of 2022 and occupies 1,886,068 square kilometres (728,215 square miles), making it Africa's third-largest country by area, and the third-largest by area in the Arab League. It was the largest country by area in Africa and the Arab League until the secession of South Sudan in 2011, since which both titles have been held by Algeria. Its capital city is Khartoum and its most populous city is Omdurman (part of the metropolitan area of Khartoum). Sudan's history goes back to the Pharaonic period, witnessing the Kingdom of Kerma ( 2500–1500 BC), the subsequent rule of the Egyptian New Kingdom ( 1500 BC–1070 BC) and the rise of the Kingdom of Kush ( 785 BC–350 AD), which would in turn control Egypt itself for nearly a century. After the fall of Kush, the Nubians formed the three Christian kingdoms of Nobatia, Makuria, and Alodia, with the latter two lasting until around 1500. Between the 14th and 15th centuries, most of Sudan was gradually settled by Arab nomads. From the 16th to the 19th centuries, central and eastern Sudan were dominated by the Funj sultanate, while Darfur ruled the west and the Ottomans the east. During the Mamluk and Ottoman periods, slave trade played a big role and was demanded from the Sudanese Kashif as the regular remittance of tribute. In 1811, Mamluks established a state at Dunqulah as a base for their slave trading. Under Turco-Egyptian rule of Sudan after the 1820s, the practice of trading slaves was entrenched along a north–south axis, with slave raids taking place in southern parts of the country and slaves being transported to Egypt and the Ottoman empire. From the early 19th century, the entirety of Sudan was conquered by the Egyptians under the Muhammad Ali dynasty. It was under Egyptian rule that Sudan acquired its modern borders and began the process of political, agricultural, and economic development. In 1881, nationalist sentiment in Egypt led to the Orabi Revolt, "weakening" the power of the Egyptian monarchy, and