The result of World War I (1914—1918) was very important for the history of the Kurds. The Triple Entente overcame the Ottoman Empire, and the lands where Kurdish people lived before the war were separated. The lands were cut by the borders belonging to the new countries of Iraq, Turkey, and Syria. In 1916, the United Kingdom and French Third Republic had secretly agreed on how to share the territory in the Near East in the Sykes–Picot Agreement. The agreement was used to decide the borders for a long time. This was very influential and important, and stayed in the memory of Kurdish people as a betrayal by imperialism.
When the fighting was completed in World War I and the Arab Revolt, Britain and France suggested a Kurdish state could be set up. However, neither country wanted to pull back their armies from the lands that had been Ottoman (the Occupied Enemy Territory Administration). In late 1919, the French Armed Forces fought their first battle with the Kurds, in the Kurd Mountains. In this campaign ("military operation"), the French soldiers soon won victory, but they also had to fight Kurds in al-Jazira, and there they did not succeed so easily.
The British and French governments did not want to move their armies back, and because of this they said any Kurdish state would have to be in parts of Kurdistan controlled by Turkey in August 1920, when the Ottomans, British, and French all signed the Treaty of Sèvres. The Turks did not fully agree to (ratify) this treaty ("agreement between nations"), but it would have brought into existence a small independent Kurdistan under French control (suzerainty). This state, which did not become a material fact, would have been without the Kurdish lands in Iraq, Iran, or Syria.
The Turkish National Movement led by Mustafa Kemal Atatürk and the Kemalists ("supporters of Atatürk") did not agree to the Treaty of Sèvres. After they fought the Franco-Turkish War, France and Turkey signed the Treaty of Ankara in 1921. This treaty meant that the border between French-controlled Syria and the new Republic of Turkey was moved further south than had been agreed in the Treaty of Sèvres. Turkey and France both tried to make good relations with tribes in the border area, hoping that they would help to get control over the land.
In 1923, Turkey and the great powers ("most powerful nations") agreed the Treaty of Lausanne. This treaty meant that no independent Kurdistan or Kurdish state would come into existence. Instead, the Kurdish areas of the old Ottoman Empire were separated by the border between Turkey to the north, and British Iraq and French Syria to the south. The new border between Turkey and Syria was agreed to be the railway line running through the area: the part of the Berlin–Baghdad railway line that went between the cities of Aleppo and Mosul. The north side of the railway became Turkey, and the south side became French Syria. This meant that Arab areas were left in Turkey and Kurdish areas in Syria. Thomas Schmidinger, a German cultural anthropologist wrote that modern Rojava, or Syrian Kurdistan, came into existence as "a waste product of the colonial division of the Middle East" south of the Berlin–Baghdad railway line. From then until the present day, Kurdish people do not see themselves as "Syrian" or "Turkish". For Kurds in Turkey, Syria is "below the line" () on the map, but for Kurds in Syria, Turkey is "above the line" ().
On the south side of the railway line, in French Syria, some mostly Kurdish areas came under the control of France. These Kurdish areas were around the Kurd Mountains (Kurd-Dagh), around the town of Jarabulus, and the lands in Upper Mesopotamia (the Northern Jazira). They had been given to France after World War I. From the start of French control in Syria, the geography of these separated areas was very important for their later history. According to the historian Jordi Tejel, "These three Kurdish enclaves constituted … a natural extension of Kurdish territory into Turkey and Iraq".
The new borders meant that the Kurdish people in the area were divided into two groups, with two different governments. However, they were able to come and go across the border: there was at first no material separation. However, events in Turkey had deep effects on Syrian Kurds. Many Kurds ran away from Turkey in the 1920s and 1930s because of repression by the Kemalist government. The Kurds in Turkey rose up against the government in the Sheikh Said rebellion (1925) and the Ararat rebellion (1927–1930). These uprisings failed, and after them many Kurds ran away from the Turkish government, coming to live in Syria. The French government in Syria, led by the High Commissioner of the Levant in Beirut, tried to improve the profits from land in the Jazira by making these Kurdish refugees live there. The government hoped to make their control over Syria more popular in France, where the population disliked French colonialism in Syria. France's military operations were made more difficult by propaganda supporting Turkey which the Turks gave to the Kurdish and Arab tribes. There was fighting against the French in the Jazira until 1926.
The French government's settlement of Kurdish refugees in the Jazira made Kurdishness a political subject in Syria. By 1927, there were 47 villages in the Jazira whose population had a Kurdish majority. The population of Kurds and the number of Kurdish villages both increased in the 1918–1939 Interwar period ("between World War I and World War II"). The Kurds coming from outside Syrian Kurdistan meant that the Kurdish population in the Jazira increased even more.
The brothers Celadet Bedir Khan and Kamuran Alî Bedirxan started to use the Latin alphabet, which then became normal in Syrian Kurdistan and in Turkish Kurdistan. At the start, French Syria's Kurds mostly spoke Kurmanji, a Kurdish language spoken in the north of Kurdistan. In French Syria, Kurds lived both in the three enclaves of Syrian Kurdistan and outside them, in the rest of Syria. There were large Kurdish populations in the biggest cities (Aleppo and Damascus), and there were also Kurdish nomads ("people with no fixed living place") and Yazidi Kurds on the hills of Jabal Sam'an. The Kurds' lands were discontinuous and Kurdish populations were a mixture. Kurdish refugees from Turkish Kurdistan and Iraqi Kurdistan helped the Kurds become active in political work. A political movement of "pan-Kurdism" ("for all the Kurds") started to come into existence, together with different Kurdish identities.
In 1924, Kurdish delegate from the Kurd Mountains made a petition to the French Syrian government, requesting for self-rule in Kurdish-majority lands in French Syria. In 1927, Kurds from Turkish land started Xoybûn in Beirut. Xoybûn was an important pan-Kurdish political movement making early arguments for Kurdish nationalism. Xoybûn supported a military resistance in Turkish Kurdistan, but in French Syria, Xoybûn worked for self-rule in Syrian Kurdistan. Xoybûn were popular in Syrian Kurdistan and Xoybûn delegates were elected from Kurd Dagh, Jarabulus, and the Jazira in the elections of 1931. The French government refused Xoybûn's requests for self-rule.In 1936, the French government and the First Syrian Republic made an agreement on Syria's independence from France: the Franco-Syrian Treaty of Independence. World War II meant that this process was not completed. After the Battle of France, Nazi Germany occupied France, and Syria came under the control of Vichy France. When Syria was captured by the Allies of World War II in 1941's Syria–Lebanon campaign, they accepted the Syrian Republic's independence and sovereignty ("right" "to self-rule"). Xoybûn had worked all through the war, but they disbanded in 1946.