In this paper, the functions of the Nakdong River are chronologically listed as follows:
Garak State solidified its leadership of the ‘Former-Gaya’ at home by controlling the Nakdong River and intervening in trade with other inland political organizations of Gaya between 1<SUP>st</SUP>-3<SUP>rd</SUP> Century. Outwardly, Garak State strengthened its position by controlling Nakdong River in the long battles with the Silla Dynasty, which attempted to expand its power toward the Nakdong River. In this period, the river functioned as a line of communication, or waterway between several Gaya’s political organizations.
In the 4th Century, Gaya also claimed a new state name like other surrounding states. The ‘Seven States of Gaya’, shown in Chronicles of Japan (Nihonshoki), are estimated to have been located around the areas along the main stream and tributaries of the Nakdong River. At that time, the Nakdong River was believed to have been opened to Baekje ships, while being under the control of Garak State as before.
In the 5<SUP>th</SUP> Century, Gara State began to emerge as a major power after ‘Goguryeo"s Southward Conquest’. Goryeong was the core area of Gara State as it stood on the western side of the Nakdong River. This gave Gara State a natural path of expansion to Hwang River and Nam River, tributaries of Nakdong River, all under the good terms with Silla and Goguryeo. At that time, Nakdong River was also opened to Goguryeo and served as a natural border with Silla. The river still functioned as a waterway linking Gara State and other surrounding states.
Gara State ceded its territory in Gimun to Baekje between 513 and 516. Following this, Gara State began to suspect the true nature of the Silla-Baekje Alliance and began to build fortifications against a possible Silla invasion. Nakdong River then began to function as a defacto military demarcation line rather than a waterway, which demonstrated the tensions between two countries. However, given Gara?Silla Marriage Alliance in 522, the river recovered to some degree its function as a waterway. After the marriage alliance was broken off, Gara State ceded its territory in Dasajin, or Daesa to Baekje, and three castles and five northern castles to Silla in March 529. Gaya’s Takkitan, Garak, and Taksun states were annexed to Silla in 532 before and after. Afterwards, the Nakdong River functioned just as the final line of defense for Goryeong district, the core area of Gara State, and the lower reaches of the river were controlled by Silla. Thereafter, Gara fell into rapid decline.