Even if the expansion of the Seljuqs came to alarm the Christians in Europe to the extent that it helped trigger the crusader movement from the late 11th century, it was still the Shi'is who were the main enemy of the Seljuqs.
The Seljuqs made Esfahan their capital, and they started to use Persian language in the administration of the new state. The Seljuq sultans also sponsored Persian language, and they were effectively propagators of the Persian language to the entire Persian continent. Madrasas were founded to help the development of their administration, and many mosques were built. The most famous among these is the Great Mosque of Esfahan (see illustration).
The decline of the Seljuq dynasty came mainly from the practice of dividing the state between sons of sultans. This made local rule strong, but would make the Seljuq area weak for attacks from foreign powers, like the Crusaders around 1100, the Egyptians in the 12th century and the Mongols in the 13th century.
The Rum Sultanate, located to Anatolia, became the longest lasting Seljuq state. Rum was made up of peoples of different ethnic and religious origins, Christians, Armenians, Syrians and Iranian Muslims. It was state that offered its inhabitants stability and tolerance for the different groups. Commerce, agriculture and culture thrived through this period.
10th century: A group of Turkish people under the leadership of a chief called Seljuq settles in the area of the Jaxartes river (modern Kasakhstan), and convert to Islam.
11th century: Seljuqs move into the Iranian province of Khorasan.
1040: Togrul 1, chief of the Seljuqs and grandson of Seljuq, starts to conquer large parts of the lands that comprises modern Iran and Iraq.
1055: Togrul 1 conquers Baghdad from the Shi'i Buyids, and makes himself protector of the caliph in Baghdad. The caliph gives him the title sultan.
1071: Sultan Alp Arslan defeats the Byzantines at the battle of Manzikert, and took the Byzantine emperor prisoner. This alarmed the Christian Europe.
1072: Iconium is conquered from the Byzantine Empire. It is renamed Konya, and would become the seat of the Rum sultan.
1090's: With the death of Malik Shah and his vizier Nizam al-Mulk, the Seljuq state is divided into smaller states, ruled by relatives of earlier sultans.
1097: The Rum Seljuqs are defeated by the Crusaders in Asia Minor, and loses large areas to Christian rulers.
1194: Togrul 3, the last Iranian Seljuq sultan dies on the battlefield.
1230: Rum wages war against the kingdom of the Khorezmians. While Rum manages to defeat them, the open themselves up for attacks from stronger powers in the east.
1243: The last important Seljuq state, the Sultanate of Rum, is subjugated by Mongol warlords. This defined as the end of the Seljuq dynasty, even if the sultanate continued as a Mongol province.