After the establishment of diplomatic ties with the Soviet Union after the Cuban Revolution of 1959, Cuba became increasingly dependent on Soviet markets and military aid and was an ally of the Soviet Union during the Cold War. In 1972 Cuba joined the COMECON, an economic organization of states designed to create co-operation among the communist planned economies, which was dominated by its largest economy, the Soviet Union. Moscow kept in regular contact with Havana and shared varying close relations until the end of the Soviet Union in 1991. Cuba then entered an era of serious economic hardship, the Special Period.