First records of civilization in the surroundings of Viljandi date back to the 5th millennium B.C. The first written record of the earthen stronghold of Viljandi was in the year 1154 in the commentaries to al-Idrisi's world atlas Geography.
In the 12th century, a permanent settlement emerged around the stronghold of Viljandi, which also became the economic centre of the ancient Sakala district.
In 1211 the hill-fort of the Estonians in Viljandi was besieged by a joint army of Germans, Latvians, and Livs. The Livonian Sword Brethren (later the Livonian Order) captured the hill-fort in August 1223 from a contingent of the people of Rus, who joined forces with the insurgent Estonians. In place of the Sakala wooden stronghold a powerful Order Centre was started in 1224. The following year the Grand Master Volquin led the construction of the castle at the site of the former hill-fort. The Viljandi (Fellin) castle was one of the largest in the Baltic region. It was a major fortification of the Livonian Order and was appointed a commander from 1248. The fortress was continually rebuilt and modernized over the next two-hundred years.
In the 13th century, a medieval town arose on the northern side of the stronghold. The Hamburg-Riga town bylaws, lands and population of it were first recorded in 1283. During the first half of the 14th century, Viljandi joined the influential Hanseatic League – the town had become an important stop for merchants on their way to Russia and back. In 1365, the town council was party when peace between Denmark and Hansa was concluded.
In 1470, Johann Wolthus von Herse, then master of the order, took up residence in the castle. In the Middle Ages, Viljandi was a typical small commercial town, which got its main income from transit trade. The local trade and handicraft played an equally important role. In 1481, Ivan III of Russia laid siege to the castle but could not take it. The decline of Viljandi started during the
