In Constantinople, the political Kurds supported the Ottoman Empire and the constitutional government. In Ottoman Kurdistan, other Kurds were not as happy with the revolution. The CUP wanted to take away the power of the "Hamidiye". The government planned to end the existence of the "Hamidiye" itself. Many rulers from the tribes feared that they would lose their power. Many Kurds from the tribes joined local Kurdish organizations in 1908 and 1909. Although these "clubs" were part of the constitutionalist SKMP organization, they started to work against the constitutional government. The club at Bitlis started a rebellion against the CUP. After that, the government forced the clubs' existence to end. The existence of the "Hamidiye" continued, although the government took away more of its power. The government also planned to give lands to Armenian farmers, whose lands Kurdish tribes took in the past. Many Kurds started to think that constitutionalism was helping the Armenians but not helping the Kurds. Many Muslim Kurds thought the CUP was irreligious, and thought the empire was becoming weak. Italy overcame the Ottomans in the Italo-Turkish War (1911–1912). The Balkan League (Bulgaria, Greece, Serbia, and Montenegro) overcame the Ottomans in the First Balkan War (1912–1913). In these wars, the Ottoman Empire lost many lands in Africa and Europe.
Starting in 1911, Abdürrezzak Bedir Khan (another descendant of Bedir Khan Bey) was moving through Kurdistan and the Ottoman–Qajar border. He set up a network of important men from the tribes, which worked for an independent Kurdistan. Abdürrezzak Bedir Khan hoped to get help for this plan from the Russian Empire. Simko Shikak, Sheikh Taha of Nehri, and Sheikh Abdüsselam Barzani all joined Abdürrezzak Bedir Khan in having this plan. They did not start a rebellion, but they were an important danger to the government. However, the position of the Kurds in Ottoman Kurdistan and in Iranian Kurdistan changed with the start of World War I.
During World War I, Kurdistan became a battlefield. The armies of the Ottoman Empire and the Russian Empire fought in Ottoman Kurdistan and in Iranian Kurdistan. After the Battle of Sarikamish (January 1915), the Russian army took control of many Ottoman lands. Kurds fought in the Ottoman army across the empire. Many Kurds fought as conscripts in the Ottoman army against the Russian armies. Others fought in the Ottoman army in Mesopotamia. When the Ottoman Empire asked for their help, other Kurds in the tribes of Iranian Kurdistan fought against the Russian Empire there. Kurdish tribes fought for the Ottomans in the Battle of Dilman (April 1915). Other Kurds helped the Russian armies. Abdürrezzak Bedir Khan was one of those who helped the Russians. The Russian Empire made Abdürrezzak Bedir Khan governor of Erzurum when the Russians took military control of that city. Many people in the Kurdish population were persecuted by the Russian army and by Armenian partisans fighting with the Russians. Other Kurds were persecuted by the CUP Ottoman government. The government wanted to Turkify the Kurds, and in 1916, the CUP wanted the Kurdish refugees from the war to separate from one another to make Turkification more easy. Many Kurds themselves took part in the Armenian Genocide, a genocide planned by the government. Armenians were the largest minority in parts of Kurdistan before the Armenian Genocide.
After the Russian Revolutions in 1917, the Ottomans again took control over some lands Russians controlled. The Ottomans executed Abdürrezzak Bedir Khan. However, in Mesopotamia the British Empire took control of Baghdad. The British military was on its way to Mosul when the Ottoman government surrendered, and made an armistice (the Armistice of Mudros) with the Allies of World War I in October 1918. Simko Shikak took control of lands in Iranian Kurdistan near Lake Urmia. (Simko Shikak kept control of these lands until 1920.) In December 1918, Kurds in Constantinople started the Society for the Betterment of Kurdistan (SBK). The power in this organization was in two parts: a Kurdish nationalist political faction and another faction which supported the Ottoman Empire's existence. The son of Sheikh Ubeydullah, Sheikh Abdülkadir, was the leader of the Ottoman faction of the SBK. Bedir Khan Beg's son, Emin Ali Bedir Khan, was the leader of the SBK's nationalist faction.
In the north of Ottoman Kurdistan, in Anatolia, the power of Mustafa Kemal (Atatürk) was growing. Mustafa Kemal's Kemalist (Turkish nationalist) armies fought against the First Republic of Armenia. In this fight, the help of Kurds was important for the Kemalists' success. The Kemalists got help from the Kurds by saying that the Armenians wanted their land, and by saying that the Great Powers (the Allies of World War I) wanted Kurdistan to become part of the new Armenian state. In August 1919 Kurdish leaders were at the Erzurum Congress, and in September 1919 they were at the Sivas Congress.
At the Paris Peace Conference (1919–1920), the SBK's representative was Şerif Pasha. With the representatives of the Armenians, Şerif Pasha made an agreement about the lands of a new Kurdish state and the lands of a new Armenian state. A possible Kurdish state in Ottoman Kurdistan was one of the agreements in the Treaty of Sèvres (August 1920). However, other Kurds did not support the Treaty of Sèvres. They were unhappy that lands of a Muslim empire were going to have a Christian government when they became parts of Armenia. Some Kurdish leaders sent telegrams to Paris to say that they were not in agreement with the Treaty of Sèvres.
In both the south and the north of Ottoman Kurdistan, new powers were in development. In the north, the Kemalists were taking control. In the south, the British Empire was in control. The son of Said Berzinci, Sheikh Mahmud Barzanji was the leader of the Kurdish nationalists in Sulaymaniyah. The British Empire overcame the rebellion of Mahmud Barzanji, and the south of Kurdistan became part (Iraqi Kurdistan) of the new Kingdom of Iraq. In 1921, the Kemalists overcame a Kurdish rebellion (the Koçgiri rebellion) in the area of Koçgiri (near Sivas). By 1923, the Kemalist government was in control of all Anatolia. After the Kemalist armies overcame the Kingdom of Greece in the Greco-Turkish War (1919–1922), the Allies ended their Occupation of Constantinople in 1923. Then the Kemalists took control of the capital city. The new government in Constantinople ended the existence of many Kurdish organizations. Many Kurds went into exile.
As a result of the Kemalists' military success, the Treaty of Lausanne (July 1923) took the place of the Treaty of Sèvres. The Treaty of Lausanne did not set up an independent Kurdistan or give autonomy to the Kurds. The Berlin–Baghdad railway became the border between the new Turkish Republic and the French Empire. The Kurdish lands between Aleppo and Antep became part (Syrian Kurdistan) of the French Empire. The parts of Kurdistan to the north of the railway became part (Turkish Kurdistan) of the new Turkish state. The Kemalist government ended the Ottoman caliphate March 1924. The division of the Ottoman Empire's Kurds and of Ottoman Kurdistan was complete when the League of Nations gave Mosul and its Kurdish lands to the Kingdom of Iraq in 1926. The division of Kurdistan and the Kurdish population into four (Turkish Kurdistan, Iranian Kurdistan, Iraqi Kurdistan and Syrian Kurdistan) continues to exist.
In Classical Antiquity, the most important deities of the Kurds' lands were Ahura Mazda and Mithra. The most common religion was Zoroastrianism. Zoroastrianism was probably the state religion of the Achaemenid Empire. There are connections between the writings of Zoroastrianism and the Vedas, the Hindu writings of ancient India.