Oman–Saudi Arabia border

[3] Historically there was no clearly defined boundary in this part of the Arabian peninsula; at the start of the 20th century the Ottoman Empire controlled the western coast and Britain the east and south (ruled indirectly via the Sultan of Oman and local sheikhs and emirs), with the interior consisting of loosely organised Arab groupings, occasionally forming emirates, most prominent of which was the Emirate of Nejd and Hasa ruled by the al-Saud family.

[8][9] In 1955, following an attempt by Saudi Arabia to assert its control over the Buraimi Oasis on the Oman-UAE border, Britain stated that it would unilaterally use a slightly modified version of the 1935 'Riyadh line' henceforth.

[10] Following talks held in 1989, on 21 March 1990 a border treaty was signed between King Fahd of Saudi Arabia and Oman's Sultan Qaboos at Hafr al-Batin, and then ratified in May 1991.

[10] On-the-ground demarcation then followed with the assistance of the German aerial photography company Hansa Luftbild, being completed in 1995.

[citation needed] The first official border crossing, at Ramlat Khaliya in the far northern section of the frontier, was opened in 2006.