Despite the work of the commission, disputes concerning the precise boundary alignment continued. The Ottomans and Iran agreed to work on a more precise demarcation in 1911 at the urging of Russia and the Britain, both of whom had colonial aspirations in the region. From November 1913-October 1914 a boundary commission established the Constantinople Protocol, providing a detailed delimitation of the entire boundary, and also confirmed Ottoman control of the Shatt al-Arab. In general, the line was to follow the east bank of the waterway except in the region surrounding the Iranian town of Khorramshahr, where it was to follow the thalweg. The four-nation boundary commission then surveyed the border on the ground and demarcated it with pillars, producing a detailed series of map depicting the confirmed frontier.