King Munmu the Great of Silla (Hangul/Hanja: 문무대왕/文武大王; Born: 626 – Died: 681) (reigned: 661–681) whose born as Kim Beop-min (김법민/金法敏) was the thirtieth king of Silla and First King of Post-Sillan Unification. He is usually considered to have been the first ruler of the Unified Silla period. Munmu was the son of King Taejong-Muyeol the Great and Queen Munmyeong of Gimhae Kim Clan, who was the younger sister of Kim Yu-shin. Under his father's reign, he held the office of pajinchan, who apparently was responsible for maritime affairs, and played a key role in developing the country's diplomatic links with Tang China.
King Munmu took the throne in the midst of a long conflict against Baekje and Goguryeo, shortly after General Gyebaek and Baekje had been defeated at Sabi by General Kim Yu-shin in 660. In these struggles, Silla was heavily aided by the Tang. The first years of his reign were spent trying to defeat Goguryeo, following an abortive attempt in 661. Finally, in 667, he ordered another attack which led to the defeat of Goguryeo in 668. After the small isolated pockets of resistance were eliminated, Munmu was the first ruler ever to see the Korean peninsula completely unified.
King Munmu then faced the challenge of freeing his country from Tang domination. After the fall of Goguryeo, Tang created the Protectorate General to Pacify the East and attempted to place the entire Korean peninsula, including Silla, under its rule. To prevent this, Munmu forged alliances with Goguryeo resistance leaders such as Geom Mojam and Anseung, and launched a frontal attack on the Tang forces occupying former Baekje territories. The struggle lasted through the early 670s.
In 674, Tang and its former ally, Silla, were in constant battle, as King Munmu had taken over much of former Baekje and Goguryeo territory from the T'ang and fostered resistance against them. Emperor Gaozong, in anger, arbitrarily declared King Munmu's brother Kim Inmun the king Munmu and commissioned Liu Rengui with an army to attack Silla. However, King Munmu formally apologized and offered tribute, Emperor Gaozong ordered a withdrawal and recalled Kim Inmun.
In 675, Li Jinxing (李謹行) reached Silla territory with Mohe forces that submitted to Tang. However, the Tang forces were defeated by the Silla army at the Maeso fortress (Tang sources claim that the Tang forces won this and other battles in Silla).
Emperor Gaozong ordered withdrawal of Tang forces from the Korean Peninsula entirely and moved the Protectorate General to Pacify the East to Liaodong, allowing Silla to eventually expel Tang out of the Korean Peninsula and unify the parts of the peninsula south of the Taedong River. This victory, and the maintenance of Silla's independence, is generally regarded as a critical turning point in Korean history.
Munmu ruled over unified Silla for twenty years, until he fell ill in 681. On his deathbed, he left his last will and testament, and abdicated to his son, Prince Sinmun. Before he died he said: "A country should not be without a king at any time. Let the Prince have my crown before he has my coffin. Cremate my remains and scatter the ashes in the sea where the whales live. I will become a dragon and thwart foreign invasion." King Sinmun did as his father asked, and scattered his ashes over Daewangam (the Rock of the Great King), a small rocky islet a hundred metres or so off the Korean coast. Moreover, King Sinmun built the Gomun Temple (the Temple of Appreciated Blessing) and dedicated it to his father, he built a waterway for the sea dragon to come to and from the sea and land, and he built a pavilion, Eegun, overlooking the islet so that future kings could pay their respects to the great King Munmu.
In a dream, King Munmu and the famous general Kim Yu-shin appeared to King Sinmun and said to him: "Blowing on a bamboo flute will calm the heavens and the earth." King Sinmun awoke from the dream, rode out to the sea and received the bamboo flute Monposikjuk. It was said that the blowing of the bamboo flute invoked the spirits of King Munmu and General Kim Yu-shin and would push back enemy troops, cure illnesses, bring rain during drought and halt the rains in floods.
On the bus from Gyeongju to Bonggil-ri 26-beonji, Yangbuk-myeon, the sight of the vast blue sea spread before your eyes will leave you breathless. As you gaze at the glittering blue sea from Bonggil Beach, a small but particularly beautiful islet catches your eye. This little rocky islet is the Royal Underwater Tomb of King Munmu the Great, a Sillan King who unified the three kingdoms and became the 30th ruler of the Silla Kingdom. The king gave specific instructions to Kim Jeong-myeong (the future King Sinmun) to be buried in the East Sea after his death so that he would become a dragon and protect Silla from Japanese intruders.
The rocky island, about 200m in circumference, is divided by a cross-shaped waterway, forming a pool at the center, at the bottom of which is a granite 3.6 meters long, 2.9 meters wide and 0.9 meters thick. Legend has it that the remains of King Munmu’s cremated body are buried under this rock. Historians still debate whether the ashes of the King Munmu were scattered or stored in an urn and placed under the granite. The beauty of the landscape of the underwater tomb reaches its peak in autumn.