In this article, we aim to discuss whether the Yukjeong (Six Corps), a core military organization during Silla's Middle and Late Period that played a significant role in the wars of the unification of the Three Kingdoms and the Silla-Tang War, was disbanded or retained during the restructuring of Silla's military system after these wars. Even after the unification of the Three Kingdoms, the Yukjeong continued to exist without significant changes, reductions, or dissolution.
Looking at military units that used the term 'jeong' (corps), the Yukjeong appears to have been the superior command unit over the Sipjeong (Ten Corps). When examining the military officer positions within the Yukjeong and Sipjeong, it is observed that the Yukjeong included only infantry officers, whereas the Sipjeong included cavalry officers as well, indicating a complementary relationship between the two organizations. Among the Yukjeong, the Daedang (Capital Corps) in the royal capital was an exception, while the other five jeong functioned similarly to military districts. Of these five, three jeong governed a single province (ju), but the Sangjujeong (Gwidang) governed two to three provinces together.
The jurisdiction of the Yukjeong was closely linked to transportation routes connecting the royal capital and local regions, with each jeong overseeing specific waypoints along these routes. Each Yukjeong unit commanded subordinate Sipjeong units, which used the same geumsaek (unit color) system. The Sipjeong units were stationed at strategic transportation hubs originating from the royal capital, facilitating control over regions connected by main routes. The five local jeong, excluding the Daedang in the capital, managed vast military districts based on these transportation networks.
However, the Wansanjeong presented an exception. While most jeong used the same geumsaek, the Wansanjeong used white, differing from the black geumsaek of the Samryanghwajeong, Sosamjeong, and Midaburijeong. This distinction is believed to have resulted from a rebellion in Geummajeo. After suppressing the rebellion, Silla reorganized the region for surveillance and control, disbanding the Hajujeong, which governed the relatively low-risk southern region near the capital, and restructuring it into the Wansanjeong. The Wansanjeong was established with the specific purpose of monitoring rebellion and, unlike other jeong, did not command subordinate Sipjeong units.