King Sinmun (Hanja: 神文王) whose born as Kim Jeong-myeong (김정명/金政明; Reigned: 681–692) was the thirty-first king of Silla, a Korean state that originated in the southwestern Korean peninsula and went on to unify most of the peninsula under its rule in the mid 7th century. He was the eldest son of Silla's unifier-king, Munmu the Great and Queen Jaeui. He was originated from the Royal House of Gyeongju Kim. Sinmun's reign may be characterized by his attempts to consolidate royal authority following unification and to reorganize and systematize the governing appartus of the newly enlarged Silla state after conquests on Baekje in 660 and Goguryeo - eight years later.
King Sinmun was named crown prince by King Munmu the Great in 665. He came to power in the immediate wake of Silla's unification of the peninsula following its defeats of rival Baekje and Goguryeo with military aid from Tang China, and then its check of Tang ambitions to establish its hegemony over the peninsula. It was in late summer 681, not long after coming to power (the official period of mourning was in fact still in effect for the recently deceased King Munmu the Great), that a serious revolt broke out against royal authority.
The so-called "Kim Heum-dol (김흠돌/金欽突) Revolt", named after its leader, a high-ranking Silla official, though a serious challenge to royal authority on the part of a clique of aristocratic officials, also provided Sinmun with the motive to solidify his power through a purge of certain aristocrats. The causes of Kim's revolt are disputed. Kim Heum-dol was the father-in-law of Sinmun, who had married his daughter. The failure of Sinmun to produce a male heir through her, and the subsequent erosion of Kim's favor and influence at court may have been a key factor. Other scholars see in it a more serious challenge on the part of military leaders (some of whom were also implicated), who following the successful conclusion of the wars of unification saw their own influence and status erode. Still others see the source of aristocratic grievance being the rising influence of non aristocratic officials, who were increasingly being used to staff government posts. In any case, the 681 revolt was soon put down and Kim Heum-dol and those implicated were executed.
Further evidence of Sinmun's ambitious attempts to buttress central authority lies in a 689 royal edict that eliminated the official salary system, called the nogeup (녹읍/錄邑), or "stipend village", wherein in lieu of salary officials were allotted pieces of land and their attendant population whereby to extricate their income. In place of the nogeup Sinmun instituted a system wherein officials were allotted only "office land" (jikjeon/직전/職田) from which they were allowed to procure only taxes on grain. This was clearly meant to sever the landed power base of aristocratic officialdom. In time, however, this royal initiative would prove no match against an aristocracy united in its determination to protect the sources of its power. Eventually (though not in Sinmun's reign) the old stipend village system would be revived.
It was also in 689 that Sinmun made an ultimately abortive attempt to move the Silla capital from Gyeongju to Dalgubeol (달구벌/達句伐), at what is now Daegu Metropole, evidence again that Sinmun was keen on extricating the base of royal power away from the aristocratic clans, and in so doing to empower it. The Samguk Sagi, the source of this attempt at capital shifting, provides no details as to why it failed, though it is safe to assume it encountered stiff resistance by capital aristocrats.
It was following the attempted revolt Kim Heum-dol that Sinmun rescinded the fiefdom granted earlier to Anseung, the would-be king of Goguryeo, and had him come live in the Silla capital of Gyeongju in 683. Perhaps related to this, the following year Sinmun was again faced with rebellion when the general and relation to Anseung was implicated in a revolt and executed. His followers then launched the rebellion without him, seizing what is now Iksan, Northern Jeolla Province, location of Anseung's erstwhile fief. This revolt too was put down.
Sinmun's reign also saw the expansion of the Silla government and reorganization of Silla territory. Several new departments were established and for the first time were organized a system of nine national provinces (an organization that had clear allusions to the nine provinces of China during the reign of King Yu [禹王], legendary founder of the Xia Dynasty). Established as well were a series of "secondary capitals" (소경/小京), to which it was Sinmun's policy to relocate many of the peoples subjugated by the defeats of Baekje and Goguryeo. In 682 Sinmun also established the Gukhak, or National Academy, dedicated to training officials in the Confucian classics. He soon thereafter dispatched an embassy to Tang, now under the rule of Empress Wu, to request copies of the Book of Rites and other classics.
Sinmun died in 692 and buried at Neungmal Drive/Neungmal-gil, Baeban-dong 453-1 beonji, Gyeongju, Northern Gyeongsang Province. His reign weathered several serious challenges to royal authority and set the framework for the organization and governance of the expanded Silla state. The aristocratic challenges to his authority, though defeated, were harbingers of the social unrest and political upheavals that would characterize later Silla.