After it gained hold over the majority of the Korean penisnula and successfully fought off the Tang Empire, the Shilla kingdom was presented with the challenge of maintaining control over its enlarged and newly-acquired territories. In order to maintain stronger control, the Shilla monarchy strengthened its political authority and reorganized governing institutions. This was done at the expense of the aristocracy.
The Shilla kingdom was divided into nine provinces - Hanju, Sakju, Myeongju, Ungju, Sangju, Chonju, Muju, Gangju, and Yangju. Under the provincial level, areas were designated as counties. Certain cities were designated as the centers for local provincial governments. Along with the nine provinces, the islands of Ulleungdo and Usando were under the kingdom's jurisdiction and Tamnaguk (Jeju) entered a tributary relationship with Shilla.
At this time, Confucianism had already begun making its forays into the Korean peninsula and though it was not yet strongly upheld as a state ideology, it became a part of the new administrative system. As part of the drive to maintain an efficient bureaucracy, Confucian schools were also set up to instruct the nobility and future bureaucrats.
The first century of the Unified Shilla period was marked by a flowering economy and culture and a stable and strong royal authority. The prosperity of Shilla was known as far off as Egypt as Arab Muslim traders wrote of their encounters in their travels eastward.
Sources:
KBS: http://world.kbs.co.kr/english/korea/korea_history_con31.htm









