evidence: Rather than settling the border disputes between the Ottoman and Persian empires once and for all, the Treaty of Erzurum outlined the dispute that would poison the relations between the two empires and their successor states for a century and a half. Whereas the treaty implicitly confirmed the sovereignty of the Ottoman Empire over the whole Shatt al-Arab, the river which is formed by the confluence of the Tigris and Euphrates and joins them to the Persian Gulf, in Article 2 the Ottoman sultan ceded some territories on the left bank of the river, between Khorramshahr and Abadan, to the shah of Persia. In the same article, the right of free navigation from the Persian Gulf to these points was guaranteed to the Persians. Hereby the treaty helped set the margins for the future conflicts over the status of the Shatt al-Arab, which forms modern Iraq’s major outlet to the sea, and adjacent lands.