1514 (border fixed 1639)

The Battle of Chaldiran and the division of Kurdistan

The Ottomans defeat Safavid Iran, and most Kurdish princes side with the sultan, beginning a frontier that splits Kurdistan for centuries.

Battle of Chaldiran — Encyclopaedia Britannica
A Modern History of the Kurds — David McDowall, I.B. Tauris (2004)
Agha, Shaikh and State: The Social and Political Structures of Kurdistan — Martin van Bruinessen, Zed Books (1992)

Well established empirebordersself-rule

On 23 August 1514 the Ottoman sultan Selim I defeated the army of Shah Ismail, founder of Safavid Iran, on the plain of Chaldiran, north-east of Lake Van. Ottoman artillery and firearms overwhelmed the shah’s cavalry.

Battle of Chaldiran — Encyclopaedia Britannica
A Modern History of the Kurds — David McDowall, I.B. Tauris (2004)

The battle was fought on Kurdish land, and the Kurds mattered to its outcome. Ismail, a militant Shia, had alienated many of the mostly Sunni Kurdish princes, replacing some with his own governors. A Kurdish scholar and Ottoman official, Idris Bitlisi, persuaded many of them to go over to the sultan. In return, the Ottomans largely left them in charge of their own principalities, with hereditary rule, in exchange for loyalty and troops.

A Modern History of the Kurds — David McDowall, I.B. Tauris (2004)
Agha, Shaikh and State: The Social and Political Structures of Kurdistan — Martin van Bruinessen, Zed Books (1992)

The frontier moved back and forth for over a century, until the Treaty of Zuhab in 1639 fixed a line that, broadly, still separates Iran from Turkey and Iraq.

A Modern History of the Kurds — David McDowall, I.B. Tauris (2004)
Battle of Chaldiran — Encyclopaedia Britannica

The arrangement gave Kurdish emirates such as Bitlis, Botan and Baban a long golden age of semi-independence. It also split Kurdistan between two empires, and taught Kurdish leaders to survive by playing larger powers against each other. That habit served them well for centuries, and has cost them dearly in the modern era.

Agha, Shaikh and State: The Social and Political Structures of Kurdistan — Martin van Bruinessen, Zed Books (1992)
A Modern History of the Kurds — David McDowall, I.B. Tauris (2004)

Why it matters today

Kurds

The Ottoman–Iranian frontier that settled after Chaldiran still roughly divides the Kurds of Iran from those of Turkey and Iraq. It is the first great line drawn through Kurdish lands, and it gave the Kurdish emirates three centuries of autonomy as a buffer between empires.