Greece and Turkey have a long history of hostilities between each other. Greece, which was once under the rule of the Ottoman empire, only gained its independence in the 1820s. Since then, tensions have generally been high between the two nations and have resulted in military conflicts in the past, such as the Balkan wars, Greco-Turkish wars, and Turkish invasion of Cyprus. Currently, the Aegean sea dispute is at the center of Greco-Turkish tensions, with Turkey asserting that the Greek military presence on certain Aegean islands violates the 1923 Treaty of Lausanne. In response, Turkey has conducted numerous air sorties into Greek airspace, and has disputed Greek and Cypriot claims over their exclusive economic zones.