The Ilkhanate or Il-khanate was a Mongol khanate founded in the southwestern territories of the Mongol Empire. It was ruled by the Il-Khans or Ilkhanids (Persian: ایلخانان, romanized: Īlkhānān), and known to the Mongols as Hülegü Ulus (lit. 'people / state of Hülegü'). The Ilkhanid realm was officially known as the Land of Iran (Irānzamin) or simply Iran. It was established after Hülegü, the son of Tolui and grandson of Genghis Khan, inherited the West Asian and Central Asian part of the Mongol Empire after his brother Möngke Khan died in 1259.
The Ilkhanate's core territory was situated in what is now the countries of Iran, Azerbaijan, and Turkey. At its greatest extent, the Ilkhanate also included parts of modern Iraq, Syria, Armenia, Georgia, Afghanistan, Turkmenistan, Pakistan, Tajikistan, and Dagestan (Russia). Later Ilkhanid rulers, beginning with Ghazan in 1295, converted to Islam. In the 1330s, the Ilkhanate was ravaged by the Black Death. The last ilkhan, Abu Sa'id Bahadur Khan, died in 1335, after which the Ilkhanate disintegrated.
The State of the Ilkhanate was known as the Ulus of Hülegü to the Mongols during that time, as their territory was derived from one of uluses allocated to Genghis (Chinggis) Khan's descendants. The Ilkhanid rulers, although of non-Iranian origin, tried to advertise their authority by tying themselves to the Iranian past, and they recruited historians to present the Mongols as heirs to the Sasanian Empire (224–651). Native intellectuals interested in their own history interpreted the unification by the Mongols as a revival of their long-lost dynastic tradition, and the concept of "Land of Iran" (Irān-zamin) was considered an important ideology and was further developed by the later Safavid Empire (1501–1736). Similarly to the development in China under the Yuan dynasty, the revival of the concept of territorial unity, although not intended by the Mongols, became a lasting legacy of Mongol rule in Iran.
When Muhammad II of Khwarazm ordered a contingent of merchants, dispatched by the Mongols, to be killed, Genghis Khan declared war on the Anushtegin dynasty in 1219. The Mongols overran the empire, occupying the major cities and population centers between 1219 and 1221. Iran was ravaged by the Mongol detachment under Jebe and Subutai, who left the area in ruin. Transoxiana also came under Mongol control after the invasion.
Muhammad II's son Jalal al-Din Mangburni returned to Iran in c. 1224 after fleeing to India. The rival Turkic states, which were all that remained of his father's empire, quickly declared their allegiance to Jalal. He repulsed the first Mongol attempt to take Central Persia. However, Jalal al-Din was overwhelmed and crushed by Chormaqan's army sent by the Great Khan Ögedei in 1231. During the Mongol expedition, Azerbaijan and the southern Persian dynasties in Fars and Kerman voluntarily submitted to the Mongols and agreed to pay tribute.
To the west, Hamadan and the rest of Persia was secured by Chormaqan. The Mongols invaded Armenia and Georgia in 1234 or 1236, completing the conquest of the Kingdom of Georgia in 1238. They began to attack the western parts of Bagratid Armenia, which was under the Seljuks, the following year. By 1237 the Mongol Empire had subjugated most of Persia (including modern-day Azerbaijan), Armenia, Georgia (excluding Abbasid Iraq and Ismaili strongholds), as well as all of Afghanistan and Kashmir. After the Battle of Köse Dağ in 1243, the Mongols under Baiju occupied Anatolia, while the Seljuk Sultanate of Rûm and the Empire of Trebizond became vassals of the Mongols.
In 1236 Ögedei commanded Greater Khorasan to be restored and the city of Herat repopulated. The Mongol military governors mostly made camp in the Mughan plain in what is now Azerbaijan. Realizing the danger posed by the Mongols, the rulers of Mosul and the Armenian Kingdom of Cilicia submitted to the Great Khan. Chormaqan divided Transcaucasia into three districts based on the Mongol military hierarchy. In Georgia, the population was temporarily divided into eight tumens. In 1244, Güyük Khan stopped raising of revenue from districts in Persia as well and offered tax exemptions to others. In accordance with a complaint by the governor Arghun Aqa, Möngke Khan prohibited ortogh-merchants (Mongol-contracted Muslim traders) and nobles from abusing relay stations and civilians in 1251. He ordered a new census and decreed that each man in the Mongol-ruled West Asia must pay in proportion to his property. Persia was divided between four districts under Arghun. Möngke Khan granted the Kartids authority over Herat, Jam, Pushang (Fushanj), Ghor, Khaysar, Firuz-Kuh, Gharjistan, Farah, Sistan, Kabul, Tirah, and Afghanistan.
Hulegu Khan, third son of Tolui, grandson of Genghis Khan, and brother of both Möngke Khan and Kublai Khan, was the first khan of the Ilkhanate. Immediately after his brother Möngke's accession as Great Khan in 1251, Hulegu was appointed as administrator of North China, however in the following year, North China was assigned to Kublai and Hulegu tasked with conquering the Abbasid Caliphate. He was given a fifth of the entire Mongol army for the campaign and he took his sons Abaqa and Yoshmut along with him. Hulegu also took with him many Chinese scholars and astronomers, from whom the famous Persian astronomer Nasir al-Din al-Tusi learned about the mode of the Chinese calculating tables. An observatory was built on a hill of Maragheh. Taking over from Baiju in 1255, Hulegu established Mongol rule from Transoxiana to Syria. He destroyed the Nizari Ismaili state and the Abbasid Caliphate in 1256 and 1258 respectively. In 1258, Hulegu proclaimed himself ilkhan (subordinate khan). After that he advanced as far as Gaza, briefly conquering Ayyubid Syria and Aleppo in 1260. Möngke's death forced Hulegu to return to Mongolia to attend the kuriltai for the next Great Khan. He left a small force of around 10,000 behind in Palestine that was defeated at the Battle of Ain Jalut by the Mamluks of Egypt.
Due to the suspicious deaths of three Jochid princes in Hulegu's service, Berke of the Golden Horde declared war on Hulegu in 1262. According to Mamluk historians, Hulegu might have massacred Berke's troops and refused to share his war booty with Berke. Berke sought a joint attack with Baybars and forged an alliance with the Mamluks against Hulegu. The Golden Horde dispatched the young prince Nogai to invade the Ilkhanate but Hulegu forced him back in 1262. The Ilkhanid army then crossed the Terek River, capturing an empty Jochid encampment, only to be routed in a surprise attack by Nogai's forces. Many of them were drowned as the ice broke on the frozen Terek River.
In 1262, Hulegu gave Greater Khorasan and Mazandaran to Abaqa and northern Azerbaijan to Yoshmut. Hulegu himself spent his time living as a nomad in southern Azerbaijan and Armenia. During his early rule, the Ilkhanate experienced mass revolts by its subjects, with the exception of the Seljukids and Artuqids in Anatolia and Mardin. It was not until Shams al-Din Juvayni was appointed as vizier after 1262 that things started calming down and a more sustainable administration was implemented.
Hulegu fell ill in February 1265 after several days of banquets and hunting. He died on 8 February and his son Abaqa succeeded him in the summer.
Upon Abaqa's accession, he immediately faced an invasion by Berke of the Golden Horde, which ended with Berke's death in Tiflis. In 1270, Abaqa defeated an invasion by Ghiyas-ud-din Baraq of the Chagatai Khanate. Abaqa's brother Tekuder sacked Bukhara in retaliation. In 1277, the Mamluks invaded Anatolia and defeated the Mongols at the Battle of Elbistan. Stung by the defeat, Abaqa executed the local regent Mu'in al-Din Parwana and replaced him with the Mongol prince Qongqortai. In 1281, Abaqa sent Mongke Temur against the Mamluks, but he too was defeated at Homs.
Abaqa's death in 1282 triggered a succession struggle between his son Arghun, supported by the Qara'unas, and his brother Tekuder, supported by the Chinggisid aristocracy. Tekuder was elected khan by the Chinggisids. Tekuder was the first Muslim ruler of the Ilkhanate but he made no active attempt to proselytize or convert his realm. However he did try to replace Mongol political traditions with Islamic ones, resulting in a loss of support from the army. Arghun used his religion against him by appealing to non-Muslims for support. When Tekuder realized this, he executed several of Arghun's supporters, and captured Arghun. Tekuder's foster son, Buaq, freed Arghun and overthrew Tekuder. Arghun was confirmed as ilkhan by Kublai Khan in February 1286.