Samguk Sidae (三國時代)
The "Samguk" Period refers to the "Three Kingdoms" Period of Korean history (not to be confused with the Chinese "Sanguo" Period of the Romance of the Three Kingdoms 三國演義 novel). What we know of the Korean "Samguk" Period comes from Chinese historical records, particularly those of the Tang and Song Dynasties, Japanese histories, and the Korean Samguk Sagi 삼국사기.
The long period of competition between various regional powers on the Korean Peninsula and also including the now-Chinese region of Jilin and Liaoning Provinces stretched from the first century BCE at the emergence of the three regional powers to 668 CE when the kingdom of Shilla established hegemony over the region and began the Unified Shilla period. In this time period, the political situation shifted as Korean states were no longer under the more direct political control of the Chinese. Though there were several confederacies, chiefdoms, and kingdoms also existing on the Korean Peninsula in this time period, the three major states of the Samguk Period were the kingdoms of Shilla 신라, Goguryeo 고구려, and Baekje 백제.
In conjunction to the flowering of the three kingdoms, which would prove instrumental in the development of the identity of "Korean" civilization thereby leaving a lasting legacy that resonates strongly to this day, the region of East Asia experienced several dramatic developments including the waxing and waning of the mighty Han Dynasty 漢朝 in China, the virtual Rome of the East, and the rise of the Yamato 大和, who would lay the foundations of what we now call "Japan." The dynamic relationship between these regions and civilizations with the Korean peninsula and its inhabitants notably being geographically - and at times both economically and politically - in the middle brought significant changes that shaped the character of each actor involved.
...more about the Samguk Period coming soon.
-A New History of Korea. Lee, Ki-baik.
-KoreanHistoryProject.Org (Korea in the Eye of the Tiger)
-Sources of Korean Tradition. Lee, Peter H. and Wm. Theodore de Barry