The war triggered by the Japanese invasion of the Joseon Dynasty was one of the fiercest wars in history involving the 3 nations of Joseon, Japan and the Myeong Dynasty. Yeosu-si in Jeonla-namdo, where the navy command of Jeonla Left Province(abbreviation: Jeonla left navy headuarters) was seated, played the pivotal role during the war, and the Cholla left-headquarters was the main fleet at that time.
This role played by Jeonla-namdo led to the preservation of Jeonla-do, and the victory of Imjin War and Jeongyu War in Joseon Dynasty.
Admiral Yi Sun Shin described the situation at that time in this letter to Jipyeong, Hyeon, Deok-Seung of the governmental branch equivalent to today's prosecutors' office (the 26th year after Seonjo ascended to the throne):
" Honam is the fence of the nation in my view.
If Honam is lost, the entire Joseon Dynasty will disappear."
The Geobukseon Festival, a cultural event with the longest history in Korea, is held every May 04 in Yeosu. The purpose for the festival is to cultivate the spirit of protecting the nation and to commemorate the patriotism of the brave people in the '5-administration area & 5-estuaries', the eastern area of current Jeonla-namdo who were never defeated in any naval battles. Which is unprecedented in world history.
Yeosu started to be called as the headquarters of the Jeonla Left navy base when the Haenam Naval base was renamed the Jeonla Right Navy Base and the new navy base of Suncheon (currently Yeosu) was renamed the Jeonla Left navy base, since the navy barracks were set up in Naraepo-estuary in Suncheon in 1479(10th year after Seongjong ascended to the throne).
The word "Jinnamgwan" (national treasure No. 324), which was the commander of the Jeonla Left navy base, is derived from the following meaning: Jinnam is a strong word that means "suppress the South!" or "defeat and submerge Japanese battleship!". It is because Japan is located to the South from the castle city where the king resides.
The castle town fell into the hands of the enemy only 20 days after the 160,000-strong invading Japanese army conquered Busan Castle in the year of Imjin (1592). The government fled to Uiju of Pyeongando. Most of the land was completely devastated and the Dynasty was on the verge of collapse. Right at that time, Admiral Yi Sun Shin and the local people united in spirit and soul through the Jeonla Left navy base fleet and invented the Geobukseon, the world's first iron-clad ship, and prepared for war. On May 04, 1592, they made a patriotic sally against the enemy not only in Jeonla Left province, the operational theater, but also in Yongnam, scoring a great triumph in the history of naval battle, and at the same time, a remarkable triumph during the Imjin War.
Yeosu which was home to the Jeonla Left navy base and served as the headquarters of Naval Command of three provinces from 1539 to 1601, is the holy site that was witness to the patriotism to save the fatherland as the headquarters of Navy of the Joseon Dynasty over 4 centuries, and is a historic town which has kept the grand spirit and patriotism of Great Admiral Yi Sun Shin intact.