Silla began as one of the six ruling clans of Saro. Around 80 AD, the leadership of Saro was seized and consolidated by Talhae of Silla. The state of Saro began forming a confederation with neighboring walled-town states, and gradually gained strength. Saro ultimately became the Kingdom of Silla.
The reign of Pasa Isageum
In 88 AD, Silla built two forts named Gaso (가소성, 加召城), and Madu (마두성, 馬頭城), to guard against the encroachment of the Kingdom of Baekje and the Gaya confederacy, respectively. This led to the start of tensions with Gaya.
It was not until 94 AD that Gaya initiated hostilities against Silla. Subsequently, the two powers went to war again in 97 AD. Both of these campaigns were unsuccessful.
In the twenty-third year of the reign of King Pasa, Silla gained control over the previously independent states of Siljikgok (present-day Samcheok), Eumjipbeol (present-day northern Gyeongju), and Apdok (present-day Gyeongsan). Six years later, Silla took over the states of Biji (present-day Hapcheon), Dabeol (present-day Pohang), and Chopal (present-day Changwon) as well. These, together with U-si and Kueo-ch’il, which has been added the year before Pasa's accession, constituted a considerable increase in the territory of the Kingdom of Silla.
The reign of Jima Isageum
Under King Jima, relations with the neighboring Gaya confederacy became peaceful, following unsuccessful invasion attempts in 115 AD and 116 AD.