Egypt has one of the longest histories of any country, tracing its heritage along the Nile Delta back to the 6th–4th millennia BCE. Considered a cradle of civilisation, Ancient Egypt saw some of the earliest developments of writing, agriculture, urbanisation, organised religion and central government. Egypt was an early and important centre of Christianity, later adopting Islam from the seventh century onwards. Cairo became the capital of the Fatimid Caliphate in the tenth century, and of the Mamluk Sultanate in the 13th century. Egypt then became part of the Ottoman Empire in 1517, before its local ruler Muhammad Ali established modern Egypt as an autonomous Khedivate in 1867. The country was then occupied by the British Empire and gained independence in 1922 as a monarchy. Following the 1952 revolution, Egypt declared itself a republic, and in 1958 it merged with Syria to form the United Arab Republic, which was dissolved in 1961. Egypt fought several armed conflicts with Israel in 1948, 1956, 1967 and 1973, and occupyed the Gaza Strip intermittently until 1967. In 1978, Egypt signed the Camp David Accords, which recognised Israel in exchange for its withdrawal from the Sinai. After the Arab Spring, which led to the 2011 Egyptian revolution and overthrow of Hosni Mubarak, the country faced a protracted period of political unrest; this included the election in 2012 of a brief, short-lived Muslim Brotherhood-aligned Islamist government spearheaded by Mohamed Morsi, and its subsequent overthrow after mass protests in 2013.