On 12 May 1912, during the Italo-Turkish War of 1911-12, after the so-called "Battle of Cassos" which took place on 29 January 1912, the island was occupied by the sailors of the "Regia Marina" ship "Regina Elena". With the Treaty of Lausanne of 1923, Kasos joined the other islands of the Dodecanese in the Italian possession of the Italian Aegean Islands, and was ceded by Italy to Greece with the Paris Peace Treaties of 1947. The island formally joined the Kingdom of Greece on 7 March 1948 together with the other Dodecanese islands.