Syria and Turkey had long had a strained relationship, owing to historical Syrian claims on the Hatay Province, water disputes over the flow of the Tigris–Euphrates river system and the two nations' opposite alignments within the context of the Cold War, as Turkey had joined NATO, while Syria grew close to the Soviet Union. In the 1980s and 1990s, Syria–Turkey relations became even more strained as Syria had permitted both the establishment of Kurdistan Workers' Party camps within its territory, as well as allowed its leader, Abdullah Öcalan, to reside within the country. The PKK sought to establish an independent Kurdistan, which included areas held by Turkey and to this end fought in the Kurdish–Turkish conflict against the Turkish government. Turkish authorities classified the PKK as a terrorist group and undertook a campaign seeking to eliminate it. As part of this campaign, Turkey threatened Syria with a ground invasion, should Syria not expel the group from its territory and hand over Öcalan to Turkish authorities. The United States issued a parallel demand to Syria, in support of its Turkish ally. Syria initially rejected Turkish demands, but after considerable negotiations decided to partially agree to the end of the PKK's presence in Syria. In the runup to the agreement, the Syrian government made Öcalan leave the country, rather than hand him over to Turkish authorities, as per Turkish demands. Instead, he was placed on a plane travelling to Moscow. Following Öcalan's departure, Syria shut down PKK camps within its territory and arrested some PKK members which still had not left the country.
The agreement
The Adana Agreement was concluded between Turkey and Syria on 20 October 1998 in the Turkish city of Adana and included the following points:
Syria would not permit any activity which was deemed as "jeopardizing the security and stability" of Turkey. It would also not allow any form of financial or material support for the group to be delivered via its territory.
Syria would not allow the PKK to establish new camps, nor to take part in commercial activities within its borders.
Syria would recognize the PKK as a 'terrorist organization' and prohibit all of its activities, as well as the activities of any groups related to it, on Syrian soil.
Syria would not allow PKK members to travel through Syria to third countries.
Syria would not allow Abdullah Öcalan to re-enter its borders.
Should Syria fail to fulfil these demands, Turkey would have the right to chase PKK suspects 5 km deep into Syria across the Syria–Turkey border.
The main object of the agreement was a restoration of bilateral Syrian-Turkish relations, though the Turkish delegation insisted that full normalization would only be achieved after Syria fulfils even more demands, including a halt to what Turkey deemed as "inciting other nations which are members of the Arab League against Turkey", as well as cooperation in the arrest of Ocalan. These demands were appended as an annex to the text of the agreement. Syrian President Bashar al-Assad rejected the notion that the agreement was signed under pressure, stating that he had agreed to it as he had decided it would be best for Syria "to be friends with the Turkish people", which he thought was not reconcilable with Syrian support for Kurdish groups.
The Adana Agreement held until 2011, when overt Turkish support for the Syrian opposition in the context of the Syrian Civil War ended all goodwill between the two countries and the Syrian Government once again started supporting Kurdish groups as a counterweight to Turkish efforts in Syria. The Syrian government declared that Turkey had violated the understanding brought by the agreement by arming rebel groups inside Syria. In 2012 Turkish officials accused the Syrian government of providing direct support to the PKK. The Syrian government has since declared that it felt no longer bound by the agreement, but retained a "readiness" to return to it, if Turkey were to cease support for the Turkish-backed Free Syrian Army and other rebel armed groups in Syria, as well as withdraw its troops from the Turkish occupied areas of northern Syria. In 2019, the agreement gained new significance due to the contemporary Turkish operations in Syrian territory. The agreement was explicitly mentioned in the Second Northern Syria Buffer Zone deal.
