The Kurds share their lands with other ethnic groups. Some of the Kurds' neighbours are Turks, Arabs, Persians, Jews, Armenians, and Assyrians. In the past, some Arabic and Turkic people became Kurds by cultural assimilation. In the nationalist period, the governments of the states that control Kurdistan tried to assimilate the Kurds into Turkish, Iranian, and Arabic culture. These states (Turkey, Iran, Iraq, and Syria) also moved Turks, Persians, and Arabs into Kurdistan. The governments of these states have used genocide, ethnocide, linguicide, and ethnic cleansing against Kurds. The Soviet Union also forced Kurds from the Caucasus to migrate to Central Asia. When the Soviet Union ended, the First Nagorno-Karabakh War between Armenia and Azerbaijan affected most of the Kurds in the Caucasus.
Most Kurds are Muslims. Most are part of Sunni Islam. Most Kurds are part of the Shafi'i school of jurisprudence, but some Kurds are part of the Hanafi school. Sufism is also common among Kurds. There are also Kurds who are part of Shia Islam and Kurds who are part of Alevism. There are also Kurdish Jews and Yazidis.
The name of the Kurds is very old. The first proof of the name is from writing in Middle Persian (Pahlavi), the language of the Sasanian Empire. The name became most common after the Muslim conquests during the 7th century CE.
In the Islamic world of the early Middle Ages, the word had a loose meaning. The meaning was variable, and people gave many tribes and nomadic peoples the word Kurd. Peoples living in the mountains between Anatolia and the Iranian plateau often had the name "Kurd". In the Persian language and the Arabic language, writers during the 10th century gave the name to different ethnic groups. Some scholars make an argument that the meaning of the name was not an ethnonym at that time, because many different groups of nomads and pastoralists had the name "Kurds" during the Middle Ages. However, other scholars make the argument that the name was not the name of lifestyle or economic system (like nomadism or pastoralism) but the name of a population. This population shared a common character in linguistics, shared an area to live in, and shared a mythology. Whether the people and groups who had the name "Kurds" thought that they were a common community before the 12th century is unknown.
The history of the Kurds starts with the late Sasanian Empire and the Muslim conquest of Mesopotamia. Arab armies first fought against the Kurds in the late 630s. At that time, the Arabs overcame the tribes of Kurds in the mountains near Mosul. Arab armies took control of Mesopotamia in 637. Kurdish tribes helped the Sasanian armies fight against the Arabs in 639 and 644, but the Arabs had more success. Utba bin Farqad led the Arab armies that took control of the Shahrizor (a plain now in Sulaymaniyah Governorate, Iraqi Kurdistan) and the lands around Hulwan (a town now in Kermanshah Province, Iranian Kurdistan).
Then the Kurds came under the control of the Rashidun Caliphate and converted to Islam. The Arab Muslim armies came to Kurdistan after they took control of Ctesiphon (the capital of the Sasanian Empire) in 636. This was in the time of Umar, the second caliph of the Rashidun Caliphate. The Muslim armies attacked and overcame the cities Masibezan (near Ilam) and Hulwan (now Sarpol-e Zahab). When the armies of the Sasanian Empire and the Rashidun Caliphate met at Nahavand, they fought the Battle of Nahavand. In the battle, the Rashidun Caliphate's army overcame the army of the Sasanian Empire. The Arab armies also took control of Mosul, Shahrizor, and Urmia by force. Some places surrendered, like Mandali.
Most Kurds converted to Islam between the 7th and 9th centuries CE. The exact process of their religious conversion is unknown, but Kurds probably wanted to free themselves from the jizya, a tax on people who were not Muslims. Most became part of Sunni Islam, and most were Shafi'ites. The Kurds fought against the government at some times, but fought with the government's army at other times. Kurdish tribes made rebellions against the Rashidun Caliphate in 645 and in 659. In 666 there were two rebellions (in Ahvaz and in Fars). During the Umayyad Caliphate, Kurds made rebellions in 685, 702, and 708. Kurdish tribes fought for Marwan II (who controlled the Umayyad Caliphate) against the rebellion in 746.
When the Kurds became Muslims, they became part of the community of the Islamic world. Kurds were then able to became a part of the political and military power of the region. When the some of largest towns in the area became part of the Rashidun Caliphate (Mosul, Erbil, Shahrizor, Seymere, Borujerd, Hamadan, Dinavar, Nahavand, Siravand, and Karaj of Abu Dulaf), they became important places of education and religion during early Islam.
During the Abbasid Caliphate, there were many rebellions by Kurds. During rebellions in 840, 846, and 866, Kurds took control of Mosul. Some Kurds were part of the Zanj Rebellion (869–883) and some were part of Ya'qub ibn al-Layth as-Saffar's rebellion. The Abbasid Caliphate became weak in the 9th century, and Kurdish lords were sometimes able to take control of government in the mountains.
There were a number of Kurdish dynasties that controlled a number of emirates in the Kurdish region. The Shaddadids controlled lands in Armenia and Azerbaijan from 951 to 1174. The Rawwidids controlled lands in Azerbaijan between 955 and 1071. The Hasanwayhids controlled parts of western Iran between 959 and 1095. The Marwanids controlled the lands around Diyarbakır (a city now in Turkish Kurdistan) and Lake Van between 990 and 1096.
In the 11th century, the Seljuk dynasty and the Zengid dynasty fought wars with the Kurdish emirates. The Seljuk dynasty took control of Iran, Iraq, and Anatolia. The Zengid dynasty controlled the lands around Mosul for the Seljuks. The success of their armies ended the independence of the Kurds' emirates. When the Seljuks took control of Dvin (now in Armenia) from the Shaddadid dynasty, Shadhi ibn Marwan and his two sons Najm ad-Din Ayyub and Asad ad-Din Shirkuh worked for the Shaddadids. They went away from the city and came to Iraq. Najm ad-Din Ayyub and Asad ad-Din Shirkuh became important soldiers in the armies of Nur ad-Din Zengi, who controlled Syria and Mosul. Najm ad-Din Ayyub became governor of Baalbek and Damascus. Asad ad-Din Shirkuh became governor of Homs.
In 1163, Shirkuh led an invasion of the Fatimid Caliphate, which controlled Egypt. After this first attack, Shirkuh's Zengid army went out of Egypt in 1164, but they attacked again in 1167. This invasion had success, but after two years Shirkuh died. The son of Najm ad-Din Ayyub then took control of his uncle Shirkuh's army in Egypt. This son was Salah ad-Din Yusuf ibn Ayyub ("Saladin"). Working for Nur ad-Din Zengi, Saladin then used the Zengid army for the destruction of the Fatimid Caliphate. Doing this, Saladin ended the control of Shia Islam in Egypt and took control of Egypt himself when Nur ad-Din died in 1174.
Saladin's Ayyubid dynasty controlled many lands. Libya, the Hejaz, Yemen, Sudan, Egypt, and Syria were all under Saladin's control. Saladin also took control of many castles, and he took control of Jerusalem after the Battle of Hattin in 1187. (Jerusalem had been part of the Roman Catholic Kingdom of Jerusalem from the time of the First Crusade. Saladin took back Jerusalem for the Muslims.) Saladin died in 1193. The Ayyubid dynasty ended in 1250, when the Mamluks took control of Egypt and the Mongols attacked the Ayyubids in Syria. With the end of the Ayyubids' government in Egypt and Syria, Kurdish power there ended. (Some of the Ayyubid dynasty continued to control Hasankeyf into the 16th century.) Kurds continued to live in many lands that the Ayyubids had controlled. From this time, many Kurds lived in the Kurdish quarter of Damascus. (They spoke Kurdish there into the 20th century.)