Having invaded in 1570, Turks controlled and solely governed all of the Cyprus island from 1571 until its leasing to the British Empire in 1878. Cyprus was placed under British administration based on Cyprus Convention in 1878 and formally annexed by Britain at the beginning of World War I in 1914. While Turkish Cypriots made up 18% of the population, the partition of Cyprus and creation of a Turkish state in the north became a policy of Turkish Cypriot leaders and the Republic of Turkey in the 1950s. Politically, there was no majority/minority relation between Greek Cypriots and Turkish Cypriots; and hence, in 1960, Republic of Cyprus was founded by the constituent communities in Cyprus (Greek Cypriots and Turkish Cypriots) as a non-unitary state; the 1960 Constitution set both Turkish and Greek as the official languages. During 1963–74, the island experienced ethnic clashes and turmoil, following the Greek nationalists' coup to unify the island to Greece, which led to the eventual Turkish invasion in 1974. Turkish Republic of Northern Cyprus was declared in 1983 and recognized only by Turkey. Monroe Leigh, 1990, The Legal Status in International Law of the Turkish Cypriot and the Greek Cypriot Communities in Cyprus. The Greek Cypriot and Turkish Cypriot regimes participating in these negotiations, and the respective communities which they represent, are presently entitled to exercise equal rights under international law, including rights of self-determination. Before the Turkey's invasion in 1974, Turkish Cypriots were concentrated in Turkish Cypriot enclaves in the island.