In the mid-6th century, Silla was unable to completely control its newly acquired territory. Silla built military facilities centered on the road connecting the administrative center of Sinju and the maritime trade port with China. During this period, Iseongsanseong Fortress in Hanam, Dangseong Fortress in Hwaseong, Jukjusanseong Fortress in Anseong, and Halmisanseong Fortress in Yongin were built.
As Goguryeo began attacking Silla in the late 6th century, the situation north of the Hangang River became unstable. However, Silla thwarted Goguryeo's attempt to recover from the area north of the Hangang River through the Battle of Bukhansanseong Fortress. In this process, Silla established its rule over Sinju and intensively built military facilities to defend against Goguryeo around the early 7th century. In the area north of the Hangang River, Silla built military facilities in the Yangju Basin along the Jungnangcheon Stream and at the confluence of the Hangang River and Imjingang River. In the area south of the Hangang River, fortress were built at major strategic locations along the west coast and at the Hangang River Estuary to protect the Anyangcheon Stream and Dangseong Fortress. And to the south, military facilities were built up to the Anseongcheon Stream basin, establishing military defense system to defend administrative center of Sinju.
After the Battle of Nangbiseong, Silla moved its defense line north to the southern banks of the Imjingang River and Hantangang River to confront Goguryeo. This military defense system is significant in military history in that it was not only maintained until the fall of Goguryeo, but also provided the basis for blocking the southward advance of the Tang army during the Silla-Tang War.