This is not only a useful overview on the formation process of the Ottoman-Iran border, which eventually offered today’s Iran with its western frontiers with Turkey and Iraq, but also a good case study on the introduction of the modern Western frontier concept into Islamic Middle East states. Showing that the demarcation process in the region goes back to the Ottoman-Safavid conflicts, the author argues that the second Erzurum treaty (1847), which finally established the Ottoman-Qajar boundary, adhered fundamentally to the preceding treaties concluded between successive Iranian dynasties and the Ottomans. Among them, emphasizes the author, the treaty of Zuhāb (1639), concluded between the Safavids and the Ottomans, assumes a particular importance since it set up a far clearer frontier than the Peace of Amasya of 1555, which only drew a rough boundary between them, and gave a basic framework to later border demarcation processes. More important, according to the author, the agreements before the second Erzurum treaty were conducted based on the Islamic traditional frontier concept of ḥudūd, which draws the border as a zone rather than a line. However, in the negotiation of the second Erzurum Treaty and in the subsequent demarcation survey, under English and Russian auspices, both the Ottomans and the Qajars came to accept the modern Western concept of a clearly defined boundary line.