海洋和福建的安危密不可分，金門和澎湖又是福建海上的二座要島。其中，金門地近泉州同安內岸，控制泉、漳二府海上的交通往來，地理位置十分重要，早在明初洪武(1368-1398)時，明政府便採「佈防金門，監控泉海」的戰略思維，在島上設置守禦千戶所和巡檢司軍兵，並派浯嶼水寨兵船泊駐料羅，用來監控海上的動態。至於，孤懸大海中的澎湖，明政府則採「棄守」主張而慘遭「墟地徙民」的下場，又因海禁政策不准民人私自出海販貿或活動，致使澎湖日後演成一「失聯」的海島，爲世人所遺忘。直至嘉靖(1522-1566)晚期，澎湖成爲倭、盜入犯內地的集結處後，才再度引起明政府的關心和注意，而派遣水軍兵船前往汛防，亦讓澎湖歷史發展方向有了重大的轉折；尤其是，經隆慶(1567-1572)，再到萬曆(1573-1620)初期，澎湖倭、盜和私販巢據的問題有逐次惡化的趨勢，此又更加地增強明政府在澎湖戍防的決心，進而影響到萬曆中期澎湖遊兵的設立。而上述的這些事件，連帶使得泉州海防佈署重心發生了挪動，由金門移到澎湖，讓明代中國的海防線因澎湖的置兵而「跨越」過臺灣海峽，向東邁進了一大步。

Kin-Men and Peng-Hu Islands are two essential islands of the Fu-Jian coastal area. During the reign of Hong-Wu, 1368 AD to 1398 AD, the Ming government established a police and military force on Kin-Men Island, and stationed the navel vessels in Liao-Luo Bay, Kin-Men to defend the territorial waters. However, the Ming government abandoned its governance over Peng-Hu, which is isolated in the sea, and forced the people on Peng-Hu Island to move back to the mainland. In the later period of the reign of Jia-Jing, 1522 AD to 1566 AD, when Peng-Hu became the gathering place of pirates before they made incursions, the Ming government started to pay more attention to Peng-Hu. This was the turning point of the development of Peng-Hu, which caused the establishment of the Peng-Hu Armada in the middle period of the reign of Wan-Li, 1573 AD to 1620 AD. Besides, this event also led to the transfer of the coastal defense of Quan-Zhou area from Kin-Men to Peng-Hu Islands and moving the navel defense line to the Taiwan Strait.