Nowadays Nan-Gan Island and Bei-Gan Island are in Matsu archipelago called Gan-Tang-Shan by Ming Dynasly. Gan-Tang-Shan located on the sea out Min-Jiang estuary in Fu-Jian Province is the necessary passing position when cocmies aggressed upon Fu-Jhou City Therefore, in the beginning of Ming Dynasty, Ming government early dispatched an army to defend Gan-Tang-Shan. Later on, because Ming Dynasty must resist the Japanese pirates, it evacuated the army of Gan-Tang-Shan and migrated the inhabitants of the island to the land Afterward, Ming government set up a good deal of troops near Fu-Jhou City at the same time set up a naval base and disposed a lot of battleships in the outside of Min-Jiang estuary. Hence Gan-Tang-Shan became the most important defense strongpoint. Ming Dynasty reached the aim of protecting Fu-Jhou City by means of above-mentioned armed activities.